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DOT LIBRARY 


U.S. Department of Transportation 
Claude S. Brinegar, Secretary 


Federal Highway Administration 
Norbert T. Tiemann, Administrator 





Pa y 
ares OF 


U.S. Department of Transportation 
Federal Highway Administration 
Washington, ‘D.C. 20590 


Public Roads is published Quarterly by the 
Offices of Research and Development 


Gerald D. Love, Associate Administrator 
Editorial Staff 


Technical Editors 
C. F. Scheffey, R. C. Leathers 


Editor 
Fran Faulkner 


Assistant Editors 
Susan Bergsman, Judith Ladd 


Advisory Board 
J.W. Hess, R. H. Brink, C. L. Shufflebarger 


Managing Editor 
C. L. Potter 


Public Roads, A Journal of Highway Research and 
Development, is sold by the Superintendent of 
Documents, U.S. Government Printing Office, 
Washington, D.C. 20402, at $6.10 per year ($1.55 
additional for foreign mailing) or $1.55 per single 
copy. Subscriptions are available for 1- 

year periods. Free distribution is limited to public 
officials actually engaged in planning or 
constructing highways and to instructors of 
highway engineering. A limited number of 
vacancies are available at present 

The Secretary of Transportation has determined 
that the publication of this periodical is necessary 
in the transaction of the public business required 
by jaw of this Department. Use of funds for printing 
this periodical has been approved by the Director of 
the Office of Management and Budget through 
March 31, 1976 





Contents of this publication may be reprinted. 
Mention of source is requested. 


A JOURNAL OF HIGHWAY 
RESEARCH AND DEVELOPMENT 


September 1974 Vol. 38/No. 2 


COVER: 


Artist’s concept of Los Angeles and the State of 
California’s Division of Highway’s Experimental Traffic 
Control Program on the Santa Monica-San Diego 
Freeway. From an advertisement in the Great American 
Cities Series published by Phelps Dodge Industries, Inc. 
Artist: Robert A. Heindel. (Published with permission of 
Phelps Dodge Industries, Inc.) 








IN THIS ISSUE 


Articles 


Development of a Traffic Control Systems Handbook 


by Charles Pinnell, Dan Rosen, and Roy L. Wilshire .............. 41 
Asphalt FINGERPRINTING 
by Woodrow J. Halstead and Edward R. Oglio................... 52 


Seasonal Strength of Pavements 
by George W. Ring 


Bridge Rating and Analysis Structural System 
by Richard L. Sharp.and Webster H: Collins 33) 22 69 


Design of Open-Graded Asphalt Friction Courses 
by Richard W. Smith, James M. Rice, and Stewart R. Spelman 


Report on Accident Experience with Impact Attenuators—A Best Seller 





by John G. Viner-and Charles M. Boyer 3. [.8 30) 78 
Departments 
Our Authors)... 062.000 - ep ie ce else ee en 60 
Gerald D. Love Becomes Associate Administrator 

for Research and Development of the Federal 

Highway Administration”... 5... 5.7.4. 82) ee 49 
Implementation/User Packages .............................0).5 50 
New Research in Progress ....%.....2..5.50.5. 4.) 79 
New Publications ..... 3. o.-026.0 0.6.0.0 0 2 7 82 
Highway Research and Development Reports Available 

from National Technical Information Service.................... 83 


Map of Interstate and Defense Highways — 


Status of System Mileage, June 1974 _Inside back cover 





Development 

of a Traffic 
Control Systems 
Handbook 


by Charles Pinnell, Dan Rosen, 
and Roy L. Wilshire 


PUBLIC ROADS e Vol. 38, No. 2 


INTRODUCTION 


Urban mobility depends to a great 
extent upon surface arterial street 
systems. Traditionally, the 
intersections of these urban streets — 
and other access points along their 
routes where heavy volumes of 
conflicting traffic must be 
interchanged — have been the most 
critical elements of the system, and 
traffic signals were usually provided at 
these locations. When traffic growth 
exceeded the capacity of the surface 
streets, networks of urban freeways 
were superimposed to (1) accom- 


~ SEPEVER YO FEET EY 
DILL Aaa 
SPER Rae DO eHETS 


modate the longer through- 

trips, (2) provide for moving traffic, 
and (3) provide land access through 
interfaces with the arterial street 
network. 


Continued growth in traffic demand in 
many urban areas has resulted in 
traffic congestion and a decreased 
level of service on both types of 
facilities. As congestion occurs, an 
obvious objective is to obtain 
maximum use of the existing facilities 
and thereby forestall expensive major 
additions to, or expansion of, the 
system. 














It was in this environment that many 
agencies, both public and private, 
began searching for ways to improve 
and optimize traffic flow on urban 
streets and freeways. Many ways 

to achieve improved flow have been 
defined, including such techniques as 
one-way operation, reversible-lane 
operation, extensive on-street-parking 
prohibitions, proper allocation of 
signal green time, and minor 
regulation of influences which create 
disruptions in traffic flow, such as 
turning movements, truck loading, 
pedestrian interference, and 
restriction of access points. The 
effectiveness of traffic flow 
improvements possible through 
implementation of these basic traffic 
engineering measures has been 
demonstrated time and again by 
various research studies (1-4):! 


Italic numbers in parentheses identify the 
references on page48 


TRAFFIC CONTROL SYSTEMS—A 
DYNAMIC FIELD 


As a result of developing technology, 
new equipment—specifically the 
digital computer— is now available 
for the implementation of more 
sophisticated traffic control concepts. 
Components of typical systems are 
shown in figure 1. Such systems have 
been developed concurrently by many 
agencies, consequently there are 
several different control concepts and 
equipment configurations. 
Prospective users of these newly 
developed and developing systems 
must choose between concepts and 
techniques of control which are 
difficult, if not impossible, to 
compare. Often the prospective user 
lacks technical knowledge of —or is 
wary of —the computers and 
sophisticated communications 
techniques, which further complicates 
his choice. 


Those familiar with modern computer 
and communication technology seem 
to speak a different language with a 
totally foreign vocabulary. The 
resulting confusion sometimes leads 
to an overly Cautious approach and 
may even delay an action program 
which could prove advantageous. 


HISTORY OF SYSTEM 
DEVELOPMENT 


Urban street systems 


The development of traffic control 
signal systems parallels the 
development and use of the 
automobile. The development of 
traffic control signal systems 
depended to a great extent on the 
technology used to develop railroad 
signal systems. 


Interconnected signal systems were 
first used in 1917 in Salt Lake City 
where six intersections were manually 
controlled in a single system (5). In 
1922 in Houston, 12 intersections were 
controlled as a simultaneous system 


42 


from a central traffic tower—the first 
system to use an electric, automatic 
timer. 


Six years later, in 1928, a flexible- 
progressive fixed-time system was 
introduced. At about the same time, 
traffic-actuated local controllers using 
pressure detectors were initiated. The 
fixed-time systems were quickly 
accepted, and widespread installation 
followed until they were common in 
almost every city in this country. Their 
success was probably due to 

(1) simplicity — almost any electrician 
could understand them, (2) 

reliability —rugged components were 
used, so with minimum maintenance 
they could be installed and forgotten, 
and (3) relatively low cost. 


It was recognized that these fixed-time 
systems had limited flexibility. They 
could respond to traffic changes only 
as well as their operators could predict 
them and preset the systems to change 
on a time-clock basis. Predicting was 
difficult because of the efforts needed 
for data collection. Timing changes 
were avoided because of the effort 
required to go to each controller and 
make a change. 


As a step toward advancing the state 
of the art, an analog computer control 
system was developed and installed 
first in Denver in 1952. This system 
attempted to apply some of the 
concepts of actuated isolated 
intersection control to signalized 
networks. Sampling detectors were 
used to input traffic flow data and the 
system could adjust its timing on a 
demand, rather than time-of-day, 
basis. 


In 1960, a pilot study conducted in 
Toronto used a digital computer? 2 to 


2An IBM 650 computer with about 2,000 words 
of drurn memory —archaic by today’s standards 


3The United States Government does not 
endorse products or manufacturers. Trade or 
manufacturers’ names appear herein solely 
because they are considered essential to the 
object of this report 


September 1974 e PUBLIC ROADS 





FREEWAY SYSTEMS 


DETECTORS 


FIELD COMPONENTS 


CITY STREET SYSTEMS 


COMMUNICATION LINKS 








\ 


SS 














CENTRAL CONTROL COMPONENTS 


Figure 1.—Computer controlled traffic systems. 


perform centralized control functions 
(6,7). A fortunate byproduct was the 
amount of surveillance data made 
available by this form of control. This 
control system approach was so 
encouraging that Toronto proceeded 
with full-scale implementation, 
placing 20 intersections on-line in 
1963, expanding to about 900 
intersections under computer control 
today. 


IBM, encouraged by its evaluation of 
the market potential, began a 


PUBLIC ROADS e Vol. 38, No. 2 





cooperative effort in 1964 with the 
city of San Jose, Calif., to further 
develop a computer traffic control 
system (8). An IBM 1710 computer 
was used for this work. Control 
concepts developed and implemented 
in this project proved to be successful 
in significantly reducing stops, delays, 
and accidents. 


Beginning in 1965, Wichita Falls, Tex., 
contracted with IBM for the delivery 
of an IBM 1800 process control 
computer to be used for traffic 


43 


control. City and IBM programers 
then began a year-long effort to take 
the basic IBM 1710 programs from San 
Jose, re-code portions of them for the 
1800 computer, refine certain of the 
control algorithms, and develop an 
operational traffic control software 
package. The system was placed in 
daily operation in October 1966, 
controlling 56 central business district 
intersections, later expanded to 78 
controlled intersections. It now 
controls 85 intersections using 103 
detectors. 


2 


Figure 2.—Control room for the 
Urban Traffic Control System, 
Washington, D.C. 


Figure 3.— Chicago control center. 


Figure 4.—Chicago ramp signals. 











44 


San Jose, shortly thereafter, changed 
to the IBM 1800 computer, leading to 
the installation of similar systems in 
Austin, Portland, Fort Wayne, New 
York City, and Garland, Tex. (now 
under construction). 


The U.S. Department of 
Transportation, Federal Highway 
Administration (FHWA) recognized 
the significant advantage of the state 
of the art represented by these early 
systems, and also recognized that their 
full potential was only beginning to be 
realized. In 1969, FHWA’s Office of 
Research began the development of 
the Urban Traffic Control System 
(UTCS) project in Washington, D.C. 
(fig. 2) as an operational system to be 
used in developing, testing, and 
evaluating traffic control concepts. 
The system has been planned jointly 
by FHWA’s Traffic Systems Division, 
the District of Columbia’s Department 
of Highways and Traffic, and the 
Urban Mass Transportation 
Administration. The system has been 
developed by Sperry Systems 
Management Division (SSMD) and 
now controls 112 intersections. It is 
designed with sufficient flexibility and 
capacity to implement and evaluate 
virtually any conceivable control 
Strategy. 


Freeway systems 


In urban street systems, considerable 
control experience had been 
developed over the years since signals 
became widely used. This was not the 
case for freeways. Freeways were 
designed as free-flowing limited- 
access facilities with little advance 
consideration given to the possibility 
of needing control systems. Ever- 
increasing traffic demands and the 
resultant congestion, however, forced 
attention on methods to improve 
freeway flow. Several studies were 
performed to investigate ways to 
improve freeway operation, of which 
the works of Moskowitz (9) and Keese, 
Pinnell, and McCasland (10) are 
representative. 


September 1974 e PUBLIC ROADS 








Figure 5.—Map display room at 
traffic control center of Kanagawa 
Prefectural Police Department, 
Japan. 


The two earliest projects on freeway 
control were the Eisenhower 
Expressway project in Chicago (11)— 
figures 3 and 4—and the John Lodge 
Expressway in Detroit (72). In their 
early stages, the two projects were 
substantially different. The 
Eisenhower Expressway project 
emphasized an automatic control 
system. On the other hand, the John 
Lodge Fxpressway project emphasized 
closed-circuit television surveillance 
with intervention by human operators 
during incidents of an emergency 
nature. A variety of response 
mechanisms were studied, such as the 
closing of an entrance ramp or the 
dispatching of a patrol car to the 
scene of trouble. 


Later, in both these and other projects 
that followed, an expressway and its 
entrance and exit ramps were viewed 
as a tree network. If the objective is to 
prevent congestion on any section of 
the freeway, the system must control 
the input on one or more of the input 


ramps during periods of peak demand. 


One possible approach to freeway 
ramp control was given by 
Wattleworth and Berry (13). They 
considered a fixed origin-destination 
matrix for all points of the network 
and fixed rates of demand of entry. 
Under these assumptions, plus the 
tacit assumption of uniform mixing of 
the traffic streams at the entry points, 
maintaining the demand at all points 
of the network below a critical level is 
a problem in linear programing. 


PUBLIC ROADS e Vol. 38, No. 2 


mee EE /). 
a | 


oer N 
doe | 





__ 


Figure 6.—Map display room at 
the traffic contro! center of 
Metropolitan Expressway Public 


Corporation, Japan. 


Another approach to freeway ramp 
control proposed by Drew (14) is to 
allow a car to enter a freeway only if 
there is a gap in the entrance lane 
large enough to accommodate it. A 
fair amount of work has been done in 
developing criteria and 
instrumentation for determining 
whether or not the observed gaps are 
large enough. Other approaches are 
oriented toward balancing the sizes of 
queues at the entrance ramps. 
Finally —under the label of corrider 
control —some work is underway to 
combine the surface streets and the 
freeway into an integrated control 
system. 


These and other similar freeway 
surveillance and control systems — 
such as those on the Gulf Freeway in 
Houston, shown on page 41, and North 
Central Expressway in Dallas—have 
employed one or more of the 
following elements: 


w Closed circuit television visual 
surveillance systems. 


mw Ramp metering systems for all or 
selected ramps. 


m Lanecontrol/advisory signing 
systems (See Detroit lane contro! 
signals, page 41). 


m Traffic sensors located throughout 
the freeway for extensive surveillance 
and control use. 


gw Large map displays of the system 
under control (figs. 5, 6, and 7). 


45 


DEVELOPMENTS UNDERWAY 


From a review of the brief history of 
surveillance and control systems, it is 
obvious that this is a dynamic field. 
Technological advances have made 
tools available at reasonable costs to 
virtually remove previous limitations 
of hardware flexibility. As a result, 
significant efforts are underway to 
advance the state of the art. Some 
significant developments underway 
are briefly discussed in the following 
paragraphs: 


Urban street systems 


Urban Traffic Control System 
(UTCS)—As previously discussed, this 
installation in Washington, D.C., is 
operational and has the capability for 
implementing and testing many 
potentially constructive control 
concepts. Priority control concepts for 
buses are included in this system. 
Although first generation software is 
now operational, second and third 
generation software is being 
developed to include real-time traffic 
pattern generation and a form of 
traffic prediction ability. In all of this 
work, transferability of concepts, 
techniques, and even programs is 
stressed. As a result, first generation 
software is being coded in FORTRAN 
to enhance its use by others. 


Foreign system development — 
Development and operating 
experience with computer traffic 
control systems in other countries has 
also progressed rapidly. Some of the 





Figure 7.—The Dallas Freeway 
Corridor display. 


more noteworthy advances have been 
made in the following cities: West 
London (15-18), Central London (179), 
Munich (20-22), Hamburg (23), Madrid 
(24), Glasglow (25,26), Tokyo, Sapporo, 
and Osaka. 


NCHRP 3-18 (1)— Stanford Research 
Institute has conducted a research 
project entitled “Improved Control 
Logic for Use with Computer 
Controlled Traffic.” The project 
developed an advance control 
concept, strategy, and computer 
program (27). It included 
development of an operational 
control program for calculating offset 
patterns for a network of signalized 
intersections that has the capability 
for independent and variable split 
adjustment. The project was started in 
mid-1971 and was completed in late 
1973. San Jose’s IBM 1800 system was 
used as the development and test site. 


NCHRP 3-18 (2)— The Polytechnical 
Institute of Brooklyn is conducting 
research on a project, “Traffic Control 
in Oversaturated Street Networks.” 
One of this project’s objectives is to 
describe concepts of advanced traffic 
control techniques for improving the 
efficiency of traffic operation in 
oversaturated networks. 


City of Baltimore—The City of 
Baltimore has been engaged for 
several years in the planning and 
design of a comprehensive traffic 
control system. Design of the system is 


now complete, a contract for 
installation of the system has been 
awarded, and installation of the 
system is in progress. This project has 
contributed and will continue to 
contribute extensively to the 
technology of computer controlled 
signal systems, local controller design, 
and application of advanced solid- 
state electronic technology to the 
traffic control field. 


A report by Whitson, White, and 
Messer (28) is of immediate interest 
because it documents experiments 
with new control concepts for open 
networks. System operation and two- 
way progression were obtained while 
using multiphased actuated local 
control units capable of variable 
sequence phasing. The results showed 
remarkable improvements in system 
efficiency. 


Freeway systems 


Significant efforts are underway in the 
development and implementation of 
freeway surveillance and control 
systems. Interest in such projects is 
reflected by actions such as the 
creation, in May 1970, of a Task Force 
on Freeway Management by the Texas 
Highway Department.4 Examples of 
specific projects underway include: 





4Paper presented at HRB Freeway Operations 


Committee Meeting by Dale D. Marvel in Dallas, 


January 1972 


46 


w North Central Expressway Corridor, 
Dallas 


w Baltimore 1-83 


w Detroit City-wide System—65 
miles (104.6 km) 


mw Los Angeles— incident reporting, 
mobile TV, ramp metering? 


mw Chicago—three freeways, 90 miles 
(144.8 km) 


wm Naples, Italy (29) 


The FHWA published a 
comprehensive survey of freeway 
systems in 1973 (30), and areport on 
systems for the city street in 1972 (317). 


This brief review of the traffic control 
field provides a background for 
pinpointing the following basic 
conclusions: 


mw There is a wide range of traffic 
control applications. 


m New technology in the area of 
computer traffic control has 
developed and is still developing 
rapidly. 

m There is a broad scope of research 
and development efforts in traffic 
control, ranging from practical 
applications to sophisticated and 
theoretical studies. 

> The cover of this issue illustrates some of the 


concepts being employed on the Los Angeles 
system 


September 1974 @e PUBLIC ROADS 





m Awide range of costs and benefits 
has been calculated as indicated in 
tables 1 and 2. 


HANDBOOK DEVELOPMENT — 
RESEARCH IMPLEMENTATION 


A brief review of the developments in 
the traffic control field and an 
awareness of the need to implement 
effective traffic control techniques 
throughout the United States showed 
the necessity for a thorough study of 
the state of the art in traffic control 
and the preparation of acompendium 
of available technology, concepts, and 
practices. Such a compendium could 
foster understanding and widespread 
acceptance of existing and advanced 
traffic control techniques, leading to 
accelerated implementation and 
utilization of proven advances in 
traffic control system technology. 


In recognition of this basic need in the 
traffic control field, the Office of 
Development, FHWA, has initiated a 
project to develop a Traffic Control 
Systems Handbook. The handbook 
will document basic principles of 
traffic surveillance and control system 
design and provide detailed examples 
and illustrations of the application of 
these principles. 


The handbook is intended to serve 
many purposes and is designed for a 
wide range of users— primarily the 
practicing traffic engineer. The 
handbook will also be an important 
source document for consulting 
engineers, educators and students, and 
contractors engaged in supplying 
traffic surveillance and control 
systems. 


The project to develop a Traffic 
Control Systems Handbook is an 
example of the increased emphasis on 
implementation on the part of the 
FHWA. The FHWA has supported 
major efforts in research and 
development related to the field of 
traffic surveillance and control. These 
efforts, along with those of other 


PUBLIC ROADS e Vol. 38, No. 2 


Table 1.— Freeway system costs and benefits (30) 


Location 


Atlanta 

Minnesota 

Los Angeles 

Detroit 

Chicago 

Houston 
Local digital-gap accept- 

ance only 

Local digital-full control .. . 
Central digital-full control. . 


eee 


Annual 


net 


benefit 


Thousands 
of dollars 


24.4 
169 


oP dept 
675.0 
23185 


iki 
260.4 
8 260.4 


Equivalent 


uniform 


annual cost 


Thousands 


of dollars 
0.5 
TST 
N7e2 
49.6 
32:5 


24.8 
34.8 
40.8 


TAnnual maintenance and operating costs estimated to be $200 per ramp. 


Table 2.—City street system costs and benefits (37) 





Intersections 


Control 
strategies 


Time-of-day 


Benefit/ 
cost 
ratio 


Phot 
rede 








System 
cost 


Cost per 


intersection 


Results, 
percent reduction 


Travel |, 


time 


| Delay 





New York 
San Jose 


Arterial 

CBD! grid 
and arterial 

London 


Glasgow 
Toronto 


CBD grid and 
arterial 

Washington, D.C....... do 
(UTCS) 


Charleston, S.C. 


Fixed time 
done 


Fixed time 
Off-line 
optimiza- 
tion 
do 
Fixed time 
Variable 
split 
Fixed time 
PR type 
Pattern 
recognition 





1CBD = Central Business District. 2Not known, 3Evaluation not complete 


agencies, cities, and individuals, have 
produced significant technological 
developments. A major purpose of the 
handbook, therefore, will be to 
facilitate wide implementation of new 
traffic surveillance and control 
technology, decrease system 
installation costs, provide some 
standardization where appropriate, 
reduce system operating costs, and 
thoroughly document first generation 
systems as a foundation for 


47 


Millions 
of dollars 


0.7 
O85 


3 


Thousands 
of dollars 


1.6 
8.4 


13.0 








encouraging continued advances in 
the state of the art. 


PROJECT SCHEDULE AND PHASES 


The FHWA awarded a contract for 


handbook development, and an 18- 
month development period was begun 
in July 1973. The three major phases of 
the project are (1) data collection, 
(2) handbook preparation, and 

(3) implementation. 


The handbook will be designed to 
cover the two basic system areas — 
freeways and urban streets. The 
coverage of freeway surveillance and 
control systems will range from simple 
isolated ramp metering to freeway 
corridor control to an urban freeway 
network. Coverage of urban street 
surveillance and control systems will 
range from signalized control of an 
isolated intersection to computer 
control of a large urban street 
network. 


The data collection phase of the 
project will provide for library 
research, review of published reports, 
and the identification of sources of 
material and site locations of 
pertinent traffic control projects that 
are now operational or in the final 
development stage. The data 
collection effort will also include site 
visits, contacts with practicing traffic 
engineers, and the collection, analysis, 
and summary of all information 


pertinent to the development of the 
handbook. 


The handbook preparation phase will 
first call for the development of a 
topic outline and a comprehensive 
format. Once the topic outline and the 
comprehensive have been selected, 
the specific handbook material will be 
prepared. Extensive draft review and 
editing are planned to insure the 
quality of the final product. 


The implementation phase will 
provide for the development of a 
handbook implementation plan. This 
plan will include such items as 
training courses, workshops, and 
training aids. An initial workshop will 
be conducted as a test program and 
the results of this activity will be 
incorporated into the final 
recommendation on implementation. 


A method for periodically updating 
the handbook will be developed. The 
finished handbook plus the training 
aids should provide an excellent 
package of pertinent technology in 
the traffic control systems field. This 


package, along with a program of 
implementation, should provide for 
the rapid translation of research and 
development efforts in traffic control 


technology into practicable solutions 
for traffic control problems 
throughout the United States. 





REFERENCES 


(1) Arthur A. Carter, Jr., “Increasing the Traffic- 
Carrying Capability of Urban Arterial Streets,” 

(Wisconsin Avenue Study), U.S. Department of 
Commerce, Bureau of Public Roads, May 1962. 


(2) Walter E. Pontier, Paul W. Miller, and Walter 
H. Kraft, “Optimizing Flow on Existing Street 
Networks,’” NCHRP Report 113, Highway 
Research Board, 1971. 


(3) James H. Kell and Barnard C. Johnson, 
“Optimizing Street Operations Through Traffic 
Regulations and Control,” NCHRP Report 110, 
Highway Research Board, 1970. 


(4) Vergil G. Stover, William G. Adkins, and John 
C. Goodnight, ‘Guidelines for Medial and 
Marginal Access Control on Major Roadways,” 
NCHRP Report 93, Highway Research Board, 
1970. 


(5) Gordon M. Sessions, “Traffic Devices — 
Historical Aspects Thereof,” Institute of Traffic 
Engineers, 1971. 


(6) Neal A. Irwin, “The Toronto Computer- 
Controlled Traffic Signal System,” Traffic 
Control Theory and Instrumentation, Plenum 
Press, New York, 1965. 


(7) L. Casciato and S. Cass, ‘Pilot Study of the 
Automatic Control of Traffic Signals by a 
General Purpose Electronic Computer,” HRB 
Bulletin 338, 1962. 


(8) “San Jose Traffic Control Study,” Initial 
Report, [BM Corporation, March 1965. 


(9) K. Moskowitz, “Research on Operating 
Characteristics of Freeways,” Proceedings, 
Institute of Traffic Engineers, 1956. 


(10) C. J. Keese, Charles Pinnell, and W. R. 
McCasland, ‘A Study of Freeway Operations,” 
HRB Bulletin 235, 1960. 


(11) A. D. May, “Experimentation with Manual 
and Automatic Ramp Control,” HRB Record 59, 
1964. 


(12) E. F. Gervais, “Optimization of Freeway 
Traffic by Ramp Control,” HRB Record 59, 1964. 


(13) J. A. Wattleworth and D. S. Berry, ‘’Peak- 
Period Control of a Freeway System — Some 
Theoretical investigations,” HRB Record 89, 
1965. 


(14) Donald R. Drew, “Traffic Flow Theory and 
Control,” McGraw-Hill, 1968. 


(15) “West London Traffic Scheme,” Traffic 
Engineering and Control, January 1966. 


(16) D. A.B. Williams, “Area Traffic Control in 


West London —Assessment of First Experiment,” 
Traffic Engineering and Control, July 1969. 


48 


(17) R. Ham, “Area Traffic Control in West 
London—Vehicle Counting Detectors,” Traffic 
Engineering and Control, August 1969. 


(18) R. W. H. Attwood and D. H. Brantigan, 
“Computer Graphics for Area Traffic Control,” 
British Computer Society, Data Fair 71, 
Nottingham University, Reference 127, March 
1SYA. 


(19) K. W. Huddart and M. J. H. Chandler, ‘Area 
Traffic Control for Central London,” Traffic 
Engineering and Control, September 1970. 


(20) Werner Bolke, “Munich’s Traffic Control 
Centre,” Traffic Engineering and Control, August 
1967. 


(21) Gerhard Pavel, ‘Centralized Computer 
Control of Traffic Signals,” Traffic Engineering 
and Control, September 1967. 


(22) J. A. Ferguson, ‘Developments in West 
German Traffic Control,” Traffic Engineering and 
Control, August 1966. 


(23) Dieter Ruhnke, “Collection and Evaluation 
of Traffic Volume Data for Traffic-Dependent 
Selection of Signal Plans in Hamburg,” Siemens- 
Review, January 1969. 


(24) Antonio Valdes and Sebastian de la Rico, 
“Area Traffic Control by Computer in Madrid,” 
Traffic Engineering and Control, July 1970. 


(25) John A. Hillier, “Glasgow’s Experiment in 
Area Traffic Control,” Traffic Engineering and 
Control, December 1965. 


(26) John A. Hillier, “Equipment in the Glasgow 
Experiment,” Traffic Engineering and Control, 
February 1968. 


(27) “Improved Control Logic for Use With 
Computer-Controlled Traffic,” Interim Report, 
NCHRP Project 3-18 (1), Highway Research 
Board, July 1972. 


(28) Robert H. Whitson, Byron White, and 
Carroll J. Messer, “A Study of System Versus 
Isolated Control As Developed on the 
Mockingbird Pilot Project,” City of Dallas 
Computer Traffic Control System, February 1973. 


(29) Roberto Nenzi and Guido Anglisani, “Real- 
time Computer System Controls the Naples 
Tollway,” Traffic Engineering and Control, 
February/March 1974, p. 470. 


(30) Paul F. Everall, “Urban Freeway Surveillance 
and Control—The State of the Art,” Federa/ 
Highway Administration, Revised Edition, June 
1973 


(31) Charles R. Stockfisch, “Selecting Digital 


Computer Signal Systems,” Federal Highway 
Administration, December 1972. 


September 1974 e PUBLIC ROADS 








Pcs maven ed 


PUBLIC ROADS e Vol 






. 38, No. 2 


Gerald D. Love Becomes 
Associate Administrator for 
Research and Development 
of the Federal Highway 


Administration 


Gerald D. Love has been named 
Associate Administrator for Research 
and Development by Federal Highway 
Administrator Norbert T. Tiemann. 
Mr. Love succeeds G.W. Cleven, who 
retired in December 1973. Charles F. 
Scheffey, who had been serving as 
Acting Associate Administrator in the 
interim, will continue as Director, 
Office of Research. 


As Associate Administrator, Mr. Love 
will be the principal advisor to the 
Federal Highway Administrator on all 
research and development matters as 
they relate to FHWA missions, 
programs, and objectives. He will be 
responsible for program analysis and 
control and the administration of 
policy for the Offices of Research and 
Development. 


Mr. Love’s career with the Federal 
Highway Administration began in 
1957. He comes to Washington from 
an assignment as Regional 
Administrator for Region 5, 
Homewood, Ill. Prior to that 
assignment, he served as Regional 
Administrator for Region 1, Delmar, 
N.Y. Various other positions have 
included service in the New York and 
New Hampshire Division Offices and a 


‘special assignment working on the 


49 


Khmer American Friendship Highway 
in Phnom Penh, Cambodia. In 1968, 
Mr. Love was recognized by the U.S. 
Department of Transportation with a 
Sustained Superior Performance 
Award. 


He is a native of lowa and a graduate 
of lowa State University where he 
received both Bachelor of Science and 
Master of Science degrees. He holds a 
certificate from Yale University 
Bureau of Highway Traffic. Mr. Love 
also attended Syracuse University 
and is obtaining his doctorate from 
Rensselaer Polytechnic Institute. 
Following his B.S. degree in 1949, he 
served on active duty with the U.S. 
Navy Civil Engineer Corps in the 
Pacific Theater. He is presently a 
captain in the Navy Civil Engineer 
Corps Reserve. 


Mr. Love is a registered professional 
engineer in the States of New York and 
lowa. He is a Fellow of the American 
Society of Civil Engineers and a 
member of the Institute of Traffic 
Engineers. 


He and his wife, Jan, have five 
children: Laura, 21; Cynthia, 18; 
Gregory, 16; Linda, 13; and Geoffrey, 
9. They reside in Vienna, Va. 





Implementation/ User Packages 


“how-to-do-it" 


The principal tool for implementing 
research and development is the 
implementation/user package which 
provides “how-do-it” information to 
the potential user. The package 
converts research findings into 
practical tools. The packaging 
requirement is accomplished between 
the identification and promotion 
stages of implementation. 


The following items are brief 
descriptions of selected packages 
which are actively being developed, or 
have been recently completed, by 
State and Federal highway units in 
cooperation with the Implementation 
Division, Offices of Research and 
Development, Federal Highway 
Administration (FHWA). Completed 
packages will be available from the 
Implementation Division unless 
otherwise indicated. Those placed in 
the National Technical Information 
Service (NTIS) will be announced in 
this department after an NTIS 
accession number is assigned. 


U.S. Department of Transportation 
Federal Highway Administration 
Office of Development 
implementation Division, HDV-20 
Washington, D.C. 20590 


Packages Completed 


Michigan Noise Model 
by FHWA Implementation Division 


The State of Michigan has recently 
completed updating and expanding 
the original version of the noise 
prediction computer program which 
was based upon NCHRP Report 117. 
The original program was distributed 
to all of the State highway 
departments by the Federal Highway 
Administration in May 1972. This 
modified version incorporates the 
methodology contained in the new 
NCHRP Report 144. The current 
implementation effort includes 
conversion of the program from time- 
share mode to batch mode, program 
testing and evaluation, modification 
of user instructions to reflect the 
program conversion, and nationwide 
distribution. 


HIGHWAY 
GENERATED 





Accident Investigation Sites 
by Texas Highway Department and 
Texas Transportation Institute 


This report describes the Texas 
Highway Department'’s efforts to 
provide sites to conduct the police 


50 





accident investigation at a remote 
location rather than at the accident 
site. The remote accident 
investigation site concept eliminates 
the gaper-block phenomenon, which 
persists as long as the accident, police, 
and wrecker vehicles are visible to the 
freeway motorist. Police officers 
report that the remote accident 
investigation sites improved traffic 
operations and eliminated lengthy 
traffic delays. The investigation site is 
not moved if a fatality has occurred, if 
a crime has been committed, or when 
photographs or measurements are 
needed. 


The report describes applications, 
costs, and benefits on the Gulf 
Freeway in Houston and planned 
additional installations. Distribution 
has been made to the States and 
Federal Highway Administration field 
offices by the Offices of Research and 
Development, where a small number 
of additional copies are available on 
request. Copies are also available for 
$5.75 for paper copy and $1.45 for 
microfiche through the National 





oe’ 


gots ” 


Vehicles moved to remote accident 
investigation site—minor city street. 


September 1974 @ PUBLIC ROADS 








: 
) 
) 





Technical Information Service, 5285 
Port Royal Road, Springfield, Va. 
22151 by requesting Stock No. PB 
223583. 


F ACCiDENT 
| IRVESTIGATION 
f. BTE2 


a i 





Directional sign indicating route to 
remote accident investigation site. 





The following completed packages, 
announced in previous issues of 
Public Roads, are available from the 
Implementation Division. 


Open Graded Bituminous Mixtures for 
Pavements 

Concrete Structure Surface Coatings 
Encapsulated Subgrades 

Culvert Outiet Protection Program 


Urban Traffic Control/Bus Priority 
Systems (UTCS/BPS) Brochure 


Packages in 
Preparation 





Inductive Loop Detector Operations 
Guide 
by City of Los Angeles 


The Department of Traffic, City of Los 
Angeles, has developed a systematic 
procedure for troubleshooting 
malfunctioning loop detector systems. 
The procedure is designed to isolate 
system malfunctions and determine 
their probable cause as quickly and 
easily as possible, keeping 
maintenance time and disruptions to 
traffic to a minimum. The package, 
containing a description of the 
troubleshooting procedure, 
discussions of loop detector operation 
and loop system characteristics, and 
suggestions for standard loop system 
performance criteria, will provide a 
practical guide for those involved with 
loop system operation and 
maintenance. The Federal Highway 
Administration will prepare and 
reproduce the Los Angeles report for 
widespread distribution. 


The following are completed packages which were announced in 
previous issues of Public Roads and are now available from the National 
Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, 


Wap eso t. 


NTIS Accession 
Number 


title 


Texas Crash Cushion 
Trailer 


Bridge Rating and 
Analysis Structural 
System (BRASS) 


Volume |—System 
Reference 
Manual 


Volume Il—Exam- 
ple Problems 


PUBLIC ROADS ¢ Vol. 38, No. 2 


PB 231818 





Microfiche 
Price 


Paper Copy 
Price 


$3.00 $1.45 


PB 231890 


PB 231891 


51 


Breakaway Barricades 
by Nevada Department of Highways 


Urban Traffic Control/Bus Priority 
Systems (UTCS/BPS) Hardware 
Specifications 

by FHWA Implementation Division 


Aerial Drainage Survey Computer 
Program 

by Wyoming State Highway 
Department 


Water in Pavements 
by FHWA Implementation Division 





Asphalt 


FINGERPRINTING | a7 


by' Woodrow J. Halstead 
and Edward R. Oglio 


re i Y 


1) 





Under present conditions of crude oil shortages, the quantity of asphalt 
available for highway construction is likely to be reduced. The extent of 
reduction is still somewhat uncertain. Equally uncertain is the extent to 
which the quality of the available asphalt may be affected. Some States 
may be faced with the necessity of using materials from unfamiliar 
crude sources or even with modifying their specifications. For this 
reason, it appears that we should take a closer look at the usefulness of 
the system of cataloging and identifying asphalts that was developed 
under a Federal Highway Administration (FHWA) Research and 
Development Contract in 1971. Although the system is not completely 
definitive, nor foolproof, when properly employed it can provide 
valuable guidelines to those faced with evaluating the effects of 
specification changes or judging the acceptability of new materials. The 
final report of the research is published in Report No. FHWA-RD-72-18 
and is available from the National Technical Information Service (1) .2 
This article reviews some of the background and findings of this work as 
well as the rationale for the system. It is basically an abridgement of an 
article Fingerprinting of Highway Asphalts,” published by the 
Association of Asphalt Paving Technologists (AAPT) (2).° 





INTRODUCTION 


Studies of asphalt properties and 
behavior have been pursued for many 
years and have resulted in the 
production of a large quantity of 
information published in various 
papers and reports. The need for 
assembling, collating, and making this 
information available in an efficient 
manner had been recognized for some 





'Based on a paper presented at the 1972 annual 
meeting of the Association of Asphalt Paving 
Technologists, February 14-16, Cleveland, Ohio 


time. To satisfy this need, a data bank 
was set up in 1965. The bank consisted 
of a marginally punched set of cards 
containing property data accumulated 
in comprehensive surveys and studies 
of practically all asphalts produced in 
the United States in 1955-1956 and a 
broad spectrum of the 1963-1964 
production. In addition to measured 
property data, the cards contain 
information on refinery, source of 
crude, and the general refining 
procedure used in processing each 
asphalt. 


52 


After the initial organization of the 
data bank, a considerable amount of 
additional data on asphalt 
fundamental properties and 
performance-related properties 
became available. An updating and 
expansion of the cards added 
information which reflected the 
properties of more recent asphalt 
types resulting from such modern 


2\talic numbers in parentheses identify the 
references On page 59 


3The contribution of Dr. Fritz S. Rostler and Kay 


S. Rostler who prepared the major part of the text 
of the AAPT article is gratefully acknowledged 


September 1974 e PUBLIC ROADS 











production practices as blending of 
asphalts from several crudes, and use 
of combinations of refining methods. 


Also, it was apparent that the 
usefulness of the data would be 
greatly increased by a rational, 
systematized procedure for classifying 
asphalts to permit locating identical 
asphalts and asphalts of similar 
behavior characteristics from a 
specific number of property 
parameters. It was envisioned that 
such a system would serve to positively 
identify an individual, unknown 
asphalt in a manner similar to the 
identification of an individual through 
his fingerprints. Such a system would 
make it possible to predict 
performance of asphalts 
independently of crude sources, or 
methods of refining—as has been 
necessary in the past. Consequently, a 
Federal Highway Administration 
(FHWA) contract to achieve these 
ends was awarded in 1971 and a full 
report of the work accomplished is 
available from the National Technical 
Information Service (7). 


CATALOGING SYSTEM 


The cataloging system developed 
contains three similar sets of chemical 
and physical property parameters 
designated as (1) identity parameters, 
(2) fingerprint parameters, and (3) 
behavior parameters. The sets differ 
principally with respect to the limits of 
the numerical values assigned to the 
parameters. 


The identity parameters serve to group 
asphalts that are the same in all 
respects. The ranges for these 
parameters are the most restrictive, 
and essentially represent the 
variability of the test method used in 
determining an individual parameter. 


The fingerprint parameters are 
intended to identify asphalts that are 
or were the same, but which may have 
had sufficiently different histories — 
overheating, storage-aging, etc. —prior 
to measurement of the parameters to 


PUBLIC ROADS e Vol. 38, No. 2 


mask their original identity. For this 
reason, the fingerprint parameters are 
somewhat less stringent than those 
used for the identity parameters. 


The behavior parameters are the least 
stringent of the three sets and are 
intended to compare new or unknown 
asphalts with others in the bank with 
respect to performance-related 
characteristics. Asphalts placed in the 
same group by behavior parameters 
should be sufficiently similar to be 
interchangeable for highway 
construction. 


The chemical compositional 
parameters used for the identification 
systems are the compositional 
fractions of asphalt as obtained by the 
acid-precipitation method. Past 
experience has shown that this 
procedure is a reliable method for 
determining asphalt composition. As 
is well known, compositional data are 
also available from determinations 
made with other analytical procedures 
utilizing liquid chromatography, gas 
chromatography, selective solvent 
extractions, etc. Since reliable acid- 
precipitation compositional data were 
available on more asphalts than were 
available from all other analytical 
methods combined, this procedure 
was considered the most useful one 
for the present purposes. This does not 
preclude the possibility of future work 
providing a different basis for 
cataloging asphalts by chemical 
characteristics. 


The data bank and the identification | 
systems developed in the study can be 
used for cataloging and storing 
additional information and research 
results as they become available. 
Thus, past and current data will be 
available for monitoring and 
evaluating research results and as an 
aid in developing realistic 
specifications. Also, the system makes 
it possible, as described in the report, 
to predict the behavior characteristics 


53 


of new asphalts, within practical 
limits, on the basis of the system 
parameters. 


Although the identification system has 
been operative for several years, its 
potential usefulness is yet to be 
realized. To date a relatively small 
number of researchers doing work in 
the asphalt field are fingerprinting the 
asphalts being used in their research. 
It appears, however, that present 
conditions are such that greater use of 
the system could provide significant 
benefits. 


For example, by fingerprinting new 
sources of materials, States could get 
valuable predictive indications of its 
performance. Also, since present 
performance criteria are based on a 
somewhat limited spread of 
compositional differences in asphalts, 
data on new materials should 
ultimately provide a broader base for 
establishing limits in specifications. It 
may be possible to conclude that 
present requirements could be either 
broadened or made more restrictive 
on the basis of performance rather 
than on what is available. 


DATA BANK 


The asphalt data bank consists of 
individual file cards on asphalts pre- 
viously studied and described in the 
literature. The largest group Comprises 
the penetration-graded asphalts of a 
wide range of consistencies collected 
in 1954-1955 and extensively studied 
by the Bureau of Public Roads (BPR) 
(3, 4). Another large group consists of 
the viscosity-graded asphalts collected 
in 1964-1965 and studied by both the 
BPR and the Asphalt Institute (5, 6). 
Many specimens from each group 
have been included in as many as four 
or five subsequent studies by various 
investigators (7-13). 


The card file has been set up on edge- 
notched 8- by 10 1/2-inch (203- by 
266.7-mm) punched cards on each of 
which is printed a form designed to 
accommodate the most widely 
measured and most useful data on 















































| 
| 
| 






























































































































































































































































































































individual asphalts. A photograph of 
the card is shown in figure 1. The edge 
of the card is coded so that marginal 
notching makes it possible to retrieve 
cards from the file by the coded 
parameters identified in the frame 
around the edge. The file is hand 
operated, and cards are retrieved from 
the file according to coded properties 
and parameters by means of a sorting 
needle. The sorting technique is 
illustrated in figure 2. The mechanics 
of searching the card file are detailed 
in an instruction manual (14).4 





4 Data bank cards are available for purchase 
Inquiries for details should be addressed to 

Chief, Materials Division (HRS-20), Office of 
Research, Federal Highway Administration, 

Washington, D.C. 20590 








THE THREE SETS OF PARAMETERS 


It is well known that many asphalts of 
entirely different origin and chemical 
composition can meet the same 
specification requirements, such as 
penetration, viscosity, ductility, etc. 
Such data are therefore not sufficient 
for establishing identity of individual 
products. The three sets of parameters 
were based not only on the results of 
this study, but also of many preceding 
studies, and represent fundamental 
chemical and physical properties of 
the asphalts. Limits for each 
parameter are set, which determine 
whether asphalt specimens compared 
are identical, were probably once 
identical, or merely match in 
behavior. These sets of parameters — 


54 











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identity, fingerprint, and behavior — 
are presented in table 1. 


identity parameters 


The selected identity parameters 
establish identity of an asphalt to the 
extent that two specimens having the 
same numerical values (within the 
limits of experimental error) for the 
same parameters are definitely the 
same in every respect, i.e., they are 
identical. The ranges for matching 
asphalts as to identity, therefore, are 
essentially the limits of repeatability 
of the tests being used. The corollary 
from this is that two asphalts of the 
same identity characteristics will 
behave alike in every respect, when 
used in the same manner. However, 


September 1974 e PUBLIC ROADS 





; 





<3 
Ae 
ee 

2 

ts 

tS 

e 

bh 

ay 

Ee 

iS 

tS 

ts 

i 

\e 

is 

Ns 


+2] 
: 
2) 
K 
I 
a 
a 
3 
3 
= 
Sou 
aS 
Si 
ao 
ss 





Figure 2.— Data cards and sorting 
procedures. 


this does not preclude that two 
asphalts of different identity 
characteristics can give the same 
performance in laboratory tests or in 
service on the road. It is also possible 
that pavements made with the same 
asphalt will behave differently 
because of factors unrelated to the 
asphalt. 


Fingerprint parameters 


The term fingerprints is used to depict 
in one word the type of 


PUBLIC ROADS e Vol. 38, No. 2 


Table 1.— The three sets of parameters 


Measured characteristics 


Composition of asphalt 
Asphaltenes(A) 
Nitrogen bases (N) 
First acidaffins (A 4) 
Second acidaffins (A2) .... 
Paraffins (P) 
Ratio, (N+A 4)/(P+A ) 
Ratio, N/P 
Wax, 1 percent 


Range of results for matching! 


Identity Fingerprints | Behavior 


Refractive index, fractionP ......... 


Logarithm of asphalt viscosity in 
poises at 140° F (60° C) 


Penetration, 77° F (25° C), 100g, 


percentaer 


Logarithm of maltenes viscosity: 
AUF 2 E2520) 


Calo Sala lel 3.5 O1Cs) a aan 


Molecular weight of asphalt- 


poises... 
At 140° F (60° C) dOne: 
centistokes. . 


percent .. 


Weight loss in Thin Film Oven 


Pellet abrasion loss, average of unaged 
and 7-day aged... mg/revolution. . 





When the test results agree within the range indicated, the asphalts are considered to 


match for the characteristic. 


2Five to nine groups sometimes with different ranges and with some overlapping estab- 


lished. See original report (7) for details. 


3Separated into two groups; 1.0 or less and greater than 1.0. 


characterization. The fingerprints of 
an asphalt are the parameters which 
detect resemblance of specimens 
closely enough to classify them as 
originally identical. Fingerprints differ 
from the identity parameters 
principally in that some of the limits 
of the numerical values are less 
restrictive, to allow for changes which 
may have occurred in storage, shelf 
aging, or manipulation of specimens, 
e.g., heating for the withdrawal of 
samples for test. The property most 
affected by shelf aging or other 
manipulation is consistency as 
measured by either penetration or 
viscosity. Under the same conditions, 
asphalts matching in fingerprints may 


55 


not behave identically in all respects, 
but their behavior should be similar. 


Behavior parameters 


Behavior parameters are concerned 
only with performance of an asphalt. 
Asphalts need not be identical, or ever 
have been identical, to give an 
equivalent performance in service and 
in laboratory performance tests. In 
establishing the behavior parameter 
only those characteristics are included 
that have been shown to influence 
properties of the asphalt related to its 
performance. For most of the 
characteristics the full ranges of 





expected values were broken into 
groups that overlapped. Consequently, 
a given asphalt may be at the high end 
of one grouping and the low end of 
another. Thus, in its present state of 
development, use of this system 
requires some degree of subjective 
judgment. Despite these 
shortcomings, it is this set of 
parameters that could be of greatest 
benefit under the present 
circumstances—where States may be 
required to use asphalts from new or 
unfamiliar sources. Generation of the 
needed test data on new asphalts to 
compare with asphalts of known 
performance should be very useful to 
anyone faced with the necessity of 
evaluating the risks in using untried 
materials. 


RATIONALE FOR SELECTION 


Details of the rationale underlying 
selection of the specific parameters 
and limits for each of the 
characterizing systems are given in the 
full report and will not be repeated 
here. However, a discussion of the 
basic test data employed and the 
rationale for its selection is 
summarized briefly. 


Chemical composition. The method of 
expressing Composition is the acid 
precipitation method in which the 
constituents are grouped as follows: 


A —asphaltenes (the portion insoluble 
in pentane) 


N—nitrogen bases (the portion that 
reacts with 85 percent sulfuric acid) 


A1—first acidaffins (the portion that 
reacts with 98 percent sulfuric acid) 


A?—second acidaffins (the portion 
that reacts with fuming sulfuric acid) 


P—paraffins (the unreactive portion — 
saturated hydrocarbons) 


In developing the parameters the ratio 
of the more reactive constituents, 
N+A1, to the least reactive 
constituents, P+ A2, is considered a 
key factor relating to the durability of 
the asphalt. The ratio, N/P, has also 
been introduced as a factor in the 
behavior system. 


Wax content is an additional measure 
of composition, defining those 
individual components having 
crystalline structure. This additional 
characteristic is particularly useful in 
defining the nature of the two 
components A? and P. 


The refractive index of fraction P 
identifies the paraffins by the 
chemical structure and is specific for 
the three types of paraffinic 
hydrocarbons, cycloparaffins 
(naphthenes), isoparaffins (branched), 
and straight chain hydrocarbons (15, 
16). The refractive index of the 
paraffins fraction has been chosen as 
an accurately reproducible value 
definitive for an asphalt and its 
source. 


Asphalt viscosity at 140° F (60° C) has 
been chosen as an identifying 
characteristic as asphalt behavior is 
influenced not only by chemical 
reactivity of the components but also 
by consistency. 


Penetration at 77° F (25° C) has been 
used as an additional measure of 
consistency, both because it is 
descriptive of consistency at this 
temperature and because grading 
asphalts by penetration has long been 
in use, and is thus a characteristic with 
which all asphalt technologists are 
familiar. The combination of 
penetration at 77° F (25° C) and 
viscosity at 140° F (60° C) provides a 
good description of asphalt 
consistency, and the interrelation of 
the‘two is an innate characteristic of 
an asphalt. 


56 


Viscosity of the maltenes at the three 
temperatures —77° F (25° C), 140° F 
(60° C), and 275° F (135° C)—is a very 
specific characteristic of this portion 
of the asphalt. Maltenes viscosity is a 
useful identifying characteristic 
largely because of the prevalence of a 
multitude of asphalts with similar 
penetrations and asphalt viscosities. 
The 85 to 100 penetration asphalts 
included in this study, for instance, 
differed at 77° F (25° C) less than 
sevenfold in asphalt viscosity, while 
their maltenes viscosities varied over 
four hundredfold from the lowest 
value of 300 poises to the highest 
value of 130,000 poises. 


Molecular weight is an indigenous 
property of the asphaltene fraction. 
Even though not found to exert any 
great influence on asphalt behavior, 
molecular weight of the asphaltenes is 
an identifying numerical value which 
assists in defining an asphalt. 


Weight loss is an important 
characteristic of acommercial asphalt 
in the same sense as is the solids 
content of an emulsion or a cutback 
asphalt, and determines the 
proportion of the material which will 
evaporate during mixture processing 
and will not remain to serve as binder 
in the asphalt pavement. The test 
result, however, is influenced by the 
gain in weight due to oxidation of the 
asphalt. Hence, the reported test result 
may not always equal the actual 
amount of volatile matter lost. 


The pellet abrasion test has been used 
to detect abnormal behavior of an 
asphalt caused by use of additives. A 
rubberized asphalt, for instance, often 
shows much better abrasion resistance 
than an unmodified asphalt of the 
same composition, as determined by 
the fractional analysis. This 
performance test has therefore been 
included specifically to detect the 
presence of an additive which might 
result in higher abrasion resistance 
than predicted from the fractional 
composition. 


September 1974 e PUBLIC ROADS 





SPECIAL CONSIDERATIONS 
FOR FINGERPRINTS 


The requirements are different for 
fingerprinting an asphalt than for 
establishing identity. The 
fingerprinting parameters are intended 
only to establish that specimens 
analyzed have sufficient features in 
common to have originally been 
identical, even though they may have 
undergone minor changes as a result 
of shelf aging or other past history. 


The property most affected in shelf 
aging and during heating for 
liquefying samples is consistency. 
Limits for permissible differences in 
penetration and asphalt viscosity are 
therefore broader than those used in 
establishing identity. 


Minor changes during aging also occur 
in composition as measured by the 
fractional analysis. The limits set for 
fingerprinting take into account these 
expected changes in composition. 


The properties least affected by shelf 
aging are the refractive index of the 
paraffins fraction and maltenes 
viscosity. Limits for these two 
parameters have therefore been set to 
be nearly the same as for identity. It 
was an important finding that, while 
asphalt consistency can change 
considerably during storage, maltenes 
viscosity changes very little. 
Consequently, maltenes viscosity was 
chosen as a significant fingerprint 
parameter. Data are presented in the 
original report illustrating this fact. 


The changes in chemical composition 
which can occur with shelf aging were 
also demonstrated. Paraffins (P) 
content remained virtually 
unchanged. A moderate increase was 
found in asphaltenes (A) and a 
moderate change occurred in second 
acidaffins (A2). Considerably greater 
changes occurred in the most reactive 
maltenes fractions, the nitrogen bases 
(N) and the first acidaffins (A). Data 
reflecting these changes in a great 


PUBLIC ROADS e Vol. 38, No. 2 


number of specimens retained in 
storage served to establish the limits 
set up for composition parameters for 
the fingerprinting system. 


SPECIAL CONSIDERATIONS FOR 
BEHAVIOR PARAMETERS 


The behavior parameters were 
developed by establishing five to nine 
overlapping groups, sometimes with 
different ranges, for most of the 
parameters. The special grouping and 
details concerning each parameter are 
given in the full report. Briefly, the 
major considerations in selecting the 
behavior parameters are as follows: 


Composition parameters 


The exact amounts of specific 
chemical components, although 
important for identification purposes, 
are relatively unimportant in 
determining behavior of asphalts. 
Most important is the combined effect 
of the two more reactive components 
(N, A4) to the two less reactive 
components (P, A2) in the maltenes as 
expressed by the parameter 
(N+A1)/(P+A2). In a number of 
previous studies this parameter has 
been shown to be a decisive factor in 
embrittlement of asphalts upon aging, 
as measured by the pellet abrasion test 
and in field performance (7, 8, 11, 17, 
18-20). A South African study reported 
by Jamieson and Hattingh (20) is of 
particular significance, since it verifies 
the general validity of the parameter 
for asphalt currently used in that . 
country. These asphalts had not been 
investigated when the parameter was 
derived. 


The contract study demonstrated that 
the introduction of the parameter N/P, 
which is the ratio of the most reactive 
component of the maltenes to the 
least reactive one, increases accuracy 
in predicting asphalt behavior. For 
most commercial asphalts the two 
parameters run parallel. If, however, 
either N or P is unusually high, 
behavior will not follow the pattern 
predicted from the ratio 


57 


(N+A)/(P+A2). This second 
parameter (N/P) has therefore been 
introduced as an additional behavior 
parameter based on chemical 
composition. The significance of this 
parameter has been examined by an 
analysis of data on more than two 
hundred asphalts in the data bank. 


The wax in the asphalt was shown in 
the study to be related to the type of 
asphalt behavior measured by low 
temperature ductility tests. However, 
sufficient data have not yet been 
obtained to assure that the suggested 
limit of +1 percent is of general 
validity. Additional data are needed to 
establish exact limits. 


A +5 percent limit for the asphaltenes 
content is used as a behavior 
parameter and represents a 
broadening over the fingerprinting 
parameter taking into account that 
asphaltenes content, although not 
itself a critical factor in performance, 
has an effect on viscosity as a bodying 
agent. Asphaltenes content is thus by 
implication a rough indication of 
maltenes viscosity and is useful for 
characterizing asphalt when maltenes 
viscosity data are lacking. 


Consistency 


Two consistency parameters have 
been used—viscosity at 140° F (60° C) 
and penetration at 77° F (25° C). It is 
well established that products within 
the same 140° F (60° C) viscosity 
grade are more similar in flow 
characteristics during construction 
than products of the same 77° F (25° 
C) penetration grade. Accordingly, the 
characterization of an asphalt as 
belonging to one (or in some instances 
two) of nine viscosity groups at 140° F 
(60° C) is the primary identification of 
the asphalt by consistency ina 
manner similar to that used in 
specifications for viscosity graded 
asphalts. Grouping of asphalts in nine 
77° F (25° C) penetration groups 
provides a measure of consistency at 
ambient temperatures to supplement 
the viscosity at high service 





temperatures provided by the 140° F 
(60° C) viscosity. The use of both 
parameters together provides 
information regarding the temperature 
susceptibility of the asphalt. Some 
overlapping of the groups for both 
viscosity and penetration now exists 
because of the uncertainties in the 
borderline regions. 


Maltenes viscosity 


Maltenes viscosity at the two 
temperatures —77° F (25° C) and 140° 
F (60° C)—has been shown to have a 
considerable bearing on performance. 
The value for viscosity at 275° F (135° 
C) has not been included since there is 
too little difference in 275° F (135° C) 
viscosity among various maltenes to 
justify use as a parameter. Viscosity at 
77°F (25% Gpandiate 40a (60a eicor 
the maltenes fraction of an asphalt in 
a given consistency range is the 
primary factor regulating the amount 
of asphaltenes needed in an asphalt as 
a bodying agent. 


Thin Film Oven Test 


The weight loss in the Thin Film Oven 
Test (expressed as 71 percent or less 
and greater than 1 percent) was a 
useful characteristic for detecting an 
asphalt of poorer performance than 
that predictable from its composition 
parameters (7). One percent is the 
limit frequently used in specifications. 
When loss exceeds this amount, 
abnormal hardening is likely to occur. 


Pellet abrasion 


Abrasion test results are included in 
the behavior characteristics for the 
Same reason given for inclusion of this 
parameter among the fingerprint and 
identity parameters. If the 
performance of an asphalt in the 
pellet abrasion tests is better than 
predicted from the maltenes 
composition parameters, the asphalt 
should be suspected of containing an 
additive such as rubber. 


VALIDITY OF THE SYSTEM 


To determine whether the 
characterizing system and its 
respective parameters were operative, 
a total of 11 asphalt specimens were 
supplied to the contractor as 
unknowns for characterization and 
identification. 


Seven of the unknown asphalts were 
taken from storage containers that had 
been stocked from 3 to 13 years. Two 
of these seven unknowns had never 
been logged into the data bank. Three 
had been tested and logged into the 
bank, under their actual code 
numbers, prior to storage. Two were 
originally the same asphalts but had 
been stored in separate containers. 
The other four unknowns were blends 
of other asphalts in the data bank. 


All data needed to compare the 
unknowns with themselves and with 
asphalts in the data bank were 
measured and are reported in the full 
report. The report also gives details of 
the sequential sorting procedures used 
to identify the unknowns. 


In general, the contractor's search 
(sorting) was carried out by 
eliminating non-matching asphalts 
successively by each parameter. None 
of the asphalts in the data bank 
matched the unknowns with respect 
to all parameters in the jdentity series. 
The changes in composition and 
consistency were large enough to 
indicate that they could no longer be 
considered identical to the original 
asphalts as judged by the data in the 
bank. 


A comparison of the asphalts by 
fingerprint parameters correctly 
matched the five unknowns to their 
counterparts in the data bank — 
including the two unknowns that were 
the same asphalt —correctly 
concluded that unknown 2 was not in 
the bank; and indicated that unknown 
3 (which had never been logged) 


58 


might be similar to three asphalts 
already in the bank. However, this 
similarity was not considered 
conclusive since some parameter data 
were lacking on the three data bank 
asphalts. 


The remaining four unknowns (the 
blends) were newer asphalts which 
had been logged into the data bank 
and had been in storage for a 
comparatively short length of time 
(approximately 1 1/2 years). A run- 
through of the data bank using the 
identity parameters resulted in a 
correct identification of each. 


The validity of the behavior 
parameters was checked by 
comparing three pairs of asphalts with 
respect to behavior parameters and to 
performance-related laboratory tests 
such as ductility and penetration at 
low temperatures, abrasion loss, 
temperature susceptibility, etc. 


As indicated previously, the purpose 
of the behavior parameters is to 
identify or group those asphalts that 
can be expected to perform alike in 
service, within the limits of normal 
experience and expectations. Asphalts 
that match in identity parameters will 
be alike in all respects, but others 
differing in one or more identity 
characteristics may match in overall 
behavior. It is shown in the report that 
the three pairs of asphalts matching in 
behavior parameters also matched in 
the performance-related laboratory 
tests. Other data provided in the 
report.show that the pairs were not 
identical asphalts, since they did not 
match in chemical composition and 
other chemical indexes. 


SUMMARY AND CONCLUSIONS 


The work performed in the study was 
primarily to create a frame to catalog 
available information with provisions 
for incorporating future data anda 
means for predicting performance of 
asphalts from numerical values 
measured on specimens of asphalt 
cements. Those objectives were 
accomplished. 


September 1974 e PUBLIC ROADS 


Se ea 





A data bank has been set up which 
constitutes a reference file, making a 
store of information on known and 
well defined asphalts easily available 
to future investigators. The full 
potential of this file will have to be 
developed through use and through 
expansion of the file to include future 
research results on additional 
asphalts. 


Based on extensive study of the 
information in the data bank, criteria 
have been set up in the form of 
parameters for (1) determining 
identity of an asphalt, 

(2) fingerprinting, and (3) predicting 
behavior. 


There are many utilitarian 
applications besides research 
purposes for matching or identifying 
asphalts by the three sets of 
parameters. A rather prosaic 
application might be to determine 
whether two lots of asphalt delivered 
to ajob, and supposed to be the same 
asphalt, are, in fact, the same. The’ 
identity parameters will answer this 
question. Behavior parameters could 
determine whether a second lot of 
material, even though not the same 
asphalt, could be expected to give the 
same performance. The fingerprints 
will tell whether or not the asphalt was 
once the same, but altered by 
overheating. 


Another application for identifying by 
the system is in correlating and 
monitoring research results. If an 
asphalt or asphalts used in one study 
can be shown to be identical, or to 
have once been identical, to asphalts 
used in another study, results can 
legitimately be combined and their 
usefulness enlarged. Conversely, if 
asphalts in one study are not the same 
as in another, only limited 
comparisons can be made. The data 
bank can also be used by researchers 
to select asphalts for specific studies. 


PUBLIC ROADS e Vol. 38, No. 2 


Finally, it was demonstrated that 
asphalts matching in the selected 
behavior characteristics are 
equivalent for practical purposes as 
measured by tests related to 
performance. Under present 
circumstances if new asphalts or 
asphalts not normally used by a State 


can be shown to match in behavior 
parameters with asphalts of proven 
performance records, such new 
materials could be used with much 
greater confidence. Differences in 
performance might also be explained 
and predicted from differences in the 
numerical values of the parameters. 





REFERENCES 


(1) F.S. Rostler and K.S. Rostler, “Fingerprinting 
of Highway Asphalts—A Method for Cataloging 
and Identifying Highway Asphalts,” Final Re- 
port, FHWA-RD-72-18, U.S. Department of 
Transportation, Federal Highway Administration, 
November 1971, available (Stock No. PB210058) 
from the National Technical Information Service, 
5285 Port Royal Road, Springfield, Va. 22151. 


(2) F.S. Rostler, K.S. Rostler, W.J. Halstead, and 
E.R. Oglio, “Fingerprinting of Highway Asphalts,” 
Asphalt Paving Technology, vol. 41, 1972. 


(3) |. Y. Welborn and W.J. Halstead, “Properties of 
Highway Asphalts—Part |, 85-100 Penetration 
Grade,” Proceedings, Association of Asphalt 
Paving Technologists (AAPT), vol. 28, January 
1959. 


(4) |.Y. Welborn, W.J. Halstead, and J.G. Boone, 
“Properties of Highway Asphalts—Part I, Various 
Grades,” Proceedings, AAPT, vol. 29, January 
1960. 


(5) J.Y. Welborn, E.R. Oglio, and J.A. Zenewitz, 
“Viscosity-Graded Asphalt Cements,” Public 
Roads, vol. 34, No. 2, June 1966, pp. 30-42, and 
Proceedings, AAPT, vol. 35, February 1966. 


(6) V.P. Puzinauskas, “Evaluation of Properties of 
Asphalt Cements with Emphasis on Consistencies 
at Low Temperatures,” Proceedings, AAPT, 
vol. 36, February 1967 


(7) F.S. Rostler and R.M. White, “Composition and 
Changes in Composition of Highway Asphalts, 85- 
100 Penetration Grade,” Proceedings, AAPT, vol. 
31, January 1962. 


(8) W.J. Halstead, F.S. Rostler, and R.M. White, - 
“Properties of Highway Asphalts—Part III, 
Influence of Chemical Composition,” Public 
Roads, vol. 34, No. 2, June 1966, pp. 17-29, and 
Proceedings, AAPT, vol. 35, February 1966. 


(9) J. Skog, “Setting and Durability Studies on 
Paving Grade Asphalts,” Proceedings, AAPT, 
vol. 36, February 1967 


(10) A.W. Sisko and L.C. Brunstrum, “The 
Rheological Properties of Asphalts in Relation to 
Durability and Pavement Performance,” 
Proceedings, AAPT, vol. 37, February 1968. 


(11) B.A. Vallerga, R.M. White, and K.S. Rostler, 
“Changes in Fundamental Properties of Asphalts 
During Service in Pavements,” Final Report, 
Contract No. FH-11-6147, Office of Research and 
Development, U.S. Bureau of Public Roads, 
January 1970. 


] 


(12) R.J. Schmidt and L.E. Santucci, “A Practical 
Method for Determining the Glass Transition 
Temperature of Asphalts and Calculation of Their 
low Temperature Viscosities,” Proceedings, 
AAPT, vol. 35, February 1966 


(13) F. Moavenzadeh, “Asphalt Fracture,” 
Proceedings, AAPT, vol. 36, February 1967 


(14) “Instruction Manual for Use of the Asphalt 
Punch Card File Revised 1971,” Originally 
prepared by Materials Research and 
Development, Inc., under contract FH-11-7 188, for 
the Bureau of Public Roads, Federal Highway 
Administration, U.S. Department of 
Transportation, November 1971 


(15) F.S. Rostler and R.M. White, “Determination 
of Hydrocarbon Type of Petroleum Products,” 
Rubber Age 70, March 1952 


(16) ASTM Designation D 2006—70, “Standard 
Method of Test for Characteristic Groups in 
Rubber Extender and Processing Oils by the 
Precipitation Method,” 1970 Annual Book of 
ASTM Standards, Part 28, Rubber; Carbon Black; 
Gaskets, American Society for Testing and 
Materials, Philadelphia, Pa 


(17) R.M. White, W.R. Mitten, and J.B. Skog, 
“Fractional Components of Asphalts — 
Compatibility and Interchangeability of Fractions 
Produced from Different Asphalts,” Proceedings, 
AAPT, vol. 39, February 1970 


(18) —. Zube and J. Skog, “Final Report on the 
Zaca-Wigmore Asphalt Test Road,” and 
discussion by R.M. White, Proceedings, AAPT, 
vol. 38, February 1969 


(19) W.J. Gotolski, S.K. Ciesielski, and L.N. Heagy, 
“Progress Report on Changing Asphalt Properties 
of In-Service Pavements in Pennsylvania,” and 
discussion by R.M. White, Proceedings, AAPT, 
vol. 33, February 1964 


(20) I.L. Jamieson and M.M. Hattingh, “The 
Correlation of Chemical and Physical Properties 
of Bitumens with Their Road Performance,” 
(Paper No. 659), Proceedings, Australian Road 
Research Board, vol. 5, Part 5, Ramsay, Ware 
Publishing Pty. Ltd., North Melbourne, 1970 


Our Authors 


Charles Pinnell is President of Pinnell- 
Anderson-Wilshire Associates, Inc., 
Dallas, Tex. He has an extensive 
background in traffic and 
transportation research and 
development and has authored 
numerous technical articles and 
reports. Prior to entering the 
consulting field, Dr. Pinnell held 
positions with the Texas Highway 
Department and Texas Transportation 
Institute and was a senior faculty 
member of Texas A&M University. 


Dan Rosen is a highway engineer in 
the Implementation Division, Office 
of Development, Federal Highway 
Administration. He manages 
development efforts in the traffic 
engineering area and is the FHWA 
contract manager for the Traffic 
Control Systems Handbook. Prior to 
joining the Implementation Division, 
Mr. Rosen was with the Traffic 
Systems Division, Office of Research. 
He is a graduate of the FHWA training 
program 


Roy L. Wilshire is Executive Vice 
President, Pinnell-Anderson-Wilshire 
, Dallas, Tex. For 5 
years Mr. Wilshire was Director of 
Traffic and Planning for the city of 
Wichita Falls, Tex., where he 
developed and implemented one of 
the pioneering efforts in the United 
States for the control of traffic signals 
by a digital computer 


Associates, Inc 


Woodrow J. Halstead is Chief of the 
Materials Division in the Office of 
Research. He was first employed by 
the Bureau of Public Roads in 1935 
and, with the exception of 2 years in 
the Navy during World War II, has 
spent his entire career with the Federal 
Highway Administration in the field of 
research on highway materials and the 
development of test methods. He has 
been active in national technical 
groups concerned with asphalt testing 
and research such as the Association 
of Asphalt Paving Technologists, 
Transportation Research Board, and 
the American Society for Testing and 
Materials. 


Edward R. Oglio, now retired, is one of 
the country’s leading asphalt 
technologists. He was employed as a 
highway research engineer by the 
Federal Highway Administration from 
1957 until his retirement in July 1973. 
Earlier he spent 21 years at the 
National Bureau of Standards, where 
he was supervisor of their asphalt 
testing laboratory at the time of his 
transfer. 


60 








George W. Ring is a highway research 
engineer in the Structures and Applied 
Mechanics Division, Office of 
Research. Since he came to the 
Federal Highway Administration in 
1956, his work has included research 
in the fields of structural design of 
pavements, soil mechanics, and the 
structural design of pipe culverts. He 
has recently participated in a series of 
workshops across the country on 
“Water in Pavements,” conducted 
jointly by the FHWA Offices of 
Research, Development, Engineering, 
and Highway Operations. 


Richard L. Sharp is the Director of the 
Bridge Division in FHWA Region 8, 
Denver, Colo. He was the contract 
manager for the FHWA administrative 
R&D contract with the Wyoming 
Highway Department on the 
development of the Bridge Rating and 
Analysis Structural System. Mr. Sharp 
is currently serving as the contract 
manager for the BRASS Maintenance 
Service contract. He has a broad 
background in the design and 
construction of highway bridges. 


September 1974 e PUBLIC ROADS 


i 








Webster H. Collins, highway engineer 
in the Implementation Division, 
Office of Development, is the senior 
implementation manager in the area 
of structural engineering. He is 
involved with translating structural 
research findings, including traffic 
barrier systems, into operational use. 
He is experienced in the area of 
structural design and has a broad 
background in the development of 
highway engineering computer 
application programs. 


Richard W. Smith is a highway 
research engineer in the Materials 
Division, Office of Research, Federal 
Highway Administration. His research 
background and experience on 
bituminous and portland cement 
concrete materials have led him to his 
present position where he is 
responsible for the administration of a 
number of research activities in the 
skid accident reduction area. 


James M. Rice has been a research 
engineer in the Materials Division, 
Office of Research, Federal Highway 
Administration, since 1962. His career 
in the asphalt paving field spans over 
25 years and includes employment 
with the National Crushed Stone 
Association and the Natural Rubber 
Bureau. His current research efforts 
are directed toward the mechanical 
properties of asphalt paving mixtures 
and the skid resistance and wear 
resistance of pavement surfaces. 


PUBLIC ROADS e Vol. 38, No. 2 


Stewart R. Spelman is a highway 
research engineer in the Materials 
Division, Office of Research, Federal 
Highway Administration. He has 
extensive experience in research on 
design of bituminous paving mixtures 
and is responsible for conducting and 
coordinating research in this area 
under the Federally Coordinated 
Program for Research and 
Development. He is an active member 
of ASTM, being involved in work 
related to test methods for bituminous 
mixtures. 


John G. Viner has been the Chief of 
the Protective Systems Group, 
Structures and Applied Mechanics 
Division, Federal Highway 
Administration, since September 1970. 
For the past 10 years he has been 
engaged in research, having been 
associated with the development of 
impact attenuators since 1967, and 
prior to that having conducted 
structural vibration research for the 
Naval Ship Research and 
Development Center. 


61 


Charles M. Boyer is a bridge engineer 
in the Bridge Division, Office of 
Engineering, Federal Highway 
Administration, where he has been 
involved with bridge design since 
1958. From 1967 until June 1973 he 
was a structural research engineer in 
the Structures and Applied Mechanics 
Division, Office of Research, where he 
worked on bridge design details and 
impact attenuator research. 








To minimize seasonal fluctuatioris in 
the support capacity of pavements 
due to frost action, methods used to 
date include insulation of the 
subgrade, use of mechanical or 
chemical soil modifiers, replacement 
of frost susceptible soils, and control 
of water through drainage measures. 


The problem is presented and various 
solutions are discussed, with emphasis 
on improved drainage. The author 
suggests using insulated underdrains 
for removing water in the pavement 
structure during the period when some 
of the subgrade remains frozen. 


Seasonal Strength 


of Pavements 


by ' George W. Ring 


INTRODUCTION 


Highway engineers have recognized 
since Taber’s experiments in 1929 (1)? 
that increased pavement roughness 
can be caused by the formation and 
growth of ice lenses in foundation 
soils and pavement layers. Subsequent 
research and field experience have not 
only validated Taber’s explanation of 
this phenomenon, but have shown 
that there is a considerable loss of 
pavement strength when the ice 
thaws. Many other factors related to 
cold temperatures contribute to 
weakening of pavement elements. 
Some of these factors are: 


m Increased moisture content caused 
by reduced evaporation during the 
winter. 


m Increased moisture content caused 
by migration of water to the cold 
zone. 


m® Decreased density of the soil-water 
system associated with increased 
moisture content. (Actual soil density 
may increase due to dehydration 
during freezing.) 


= Temporary inhomogeneity of clay 
soils and water caused by the 


'Presented at the Symposium on Frost Action on 
Roads held at the Norwegian Road Research 
Laboratory, Oslo, Norway, October 1-3, 1973 


“Italic numbers in parentheses identify the 
reterences on page 68 


62 


formation of ice lenses in the soil- 
water system. 


Many of the factors causing weakened 
subgrades also apply to soil-aggregate 
base courses and subbase courses, 
especially when they contain even 
small amounts of material finer than 
No. 200 sieve (0.074 mm). Other 
factors important to the strength loss 
of pavements in freezing 
environments are: 


m= Water trapped in the top of a 
pavement structure when thawing of 
the ice progresses downward from the 
pavement surface. 


@ Reduced intergranular friction in 
granular base courses resulting from 
pore pressures generated by daily 
thermal expansion of air due to solar 
heating in partially saturated materials 


(2). 


w Lessened strain tolerance of 
chilled asphaltic concrete (AC) 
surface courses, although not 
necessarily a strength loss (the AC may 
actually be stronger), results in 
lessened ability of the surface to 
accommodate base course 
deflections. 


During a temporary loss in support, a 
few heavy loads can greatly shorten 
the service life of a pavement. About 
25 States make allowance for frost in 
their pavement design or take special 
steps to reduce the frost susceptibility 
of subgrade materials (3). 


September 1974 e PUBLIC ROADS 


SUBGRADE 


MOISTURE CONTENT, PERCENT 


Figure 1.—Seasonal subsurface 
conditions, loop 1 (4). 


INCREASED MOISTURE CONTENT 
OF THE SUBGRADE 


Increases in subgrade moisture during 
the winter are a primary reason for the 
increased deflections and reduced 
load capacity during the spring. Field 
moisture measurements of silty clay 
subgrade at the 1958-1960 American 
Association of State Highway Officials 
(AASHO) Road Test shows a cyclic 
seasonal fluctuation of as much as 
2 percent moisture content (fig. 1). As 
shown in figure 2, this 2 percent 
subgrade moisture variation can result 
in areduced strength (CBR) of from 50 
to 100 percent. 


Subgrade density 


Density of the AASHO Road Test 
embankment soil was about 3 lbs/ft? 
(48.3 kg/m?) less during the spring 
thaw period. This reduction in density 
from the fall value can be attributed 
partly to the increase in moisture and 
partly to the expansion of water on 
freezing. Although the change in 
density is small, it can account for a 
decrease in the strength of the 
subgrade from a CBR of 60 to a CBR of 
48 at 10 percent moisture, as shown in 
figure 2. 


PUBLIC ROADS e Vol. 38, No. 2 


MOISTURE INCREASE 
DURING THE WINTER 


Similar reductions in strength caused 
by changes in density and moisture 
were also reported for the subbase and 
base course at the AASHO Road Test 
(4), 


Entrapment of melt water over frozen 
layers 


Melt water trapped in the pavement 
structure can Create a very Critical 


UNSOAKED CORRECTED CBR, PERCENT 





condition. This has been briefly 
mentioned in the literature, but very 
little data has been accumulated. 


PORE PRESSURE DUE TO 
THERMAL EFFECTS 


Studies made at the Bureau of Public 
Roads, now Federal Highway 
Administration (FHWA), Test Track at 
Hybla Valley, Va., show that 
expansion of air in the air-water 











MOLDED DRY DENSITY, pef 
Figure 2.—CBR tests on subgrade soil (5). 


63 





150 


140 


130 


120 


110 


100 


90 






80 


70 


BEARING-PERCENT OF FALL VALUE (1952) 


Pa 


50 


0 


Pi 
Lee a. oS 
Se eee 
NEE are 
CC ere 


eed 6&A-7 SOILS 


















JAN FEB MAR APR MAY JUNE JULY AUG. SEPT OCT 


Figure 3.—Seasonal changes in 
bearing capacity (6). 


system of partially saturated 
pavements undergoing daily warming 
cycles can generate pore pressures 
which reduce inter-granular friction of 


granular base courses (2). As a result, 


pavement strength may be greatly 
reduced during the warming cycle 
until early afternoon. Conversely, 
there is a strength gain when the 
pavement cools later in the evening. 
Although this phenomenon is not 
directly related to frost action, it can 
occur during the thaw period when 
water content in the pavement 
structure is high. 


MEASUREMENT OF SEASONAL 
STRENGTH OF PAVEMENTS 


Detection and measurement of 
seasonal strength loss in pavements 
has been accomplished primarily 
through static or nearly static bearing 
tests on the subgrade through holes 
cut in the pavement surface. A few 
static bearing tests have been 
conducted on the pavement surface. 


Plate bearing (sometimes repeated), 
CBR, and the North Dakota Cone have 
been used extensively to measure 
subgrade strength (or weakness) 
during the thaw period. In the 
Northern States, spring subgrade 
strengths have been measured from 30 
to 100 percent of the fall bearing 
value, with 55 to 80 percent reported 
most often. Typical plots of seasonal 
subgrade strength as measured by 
plate bearing are shown in figure 3. 


Fewer studies have been made on the 
seasonal strength of the entire 
pavement system. Those which have 
been conducted have been primarily 
with plate bearing and the Benkleman 
Beam testing techniques. Linell (7) 
reports that the bearing capacity of 
pavement systems is constantly 
changing through the seasons of the 
year. Based on evaluations from both 
deflection measurements and 
performance observations, flexible 
pavements have only one-third of the 
strength exhibited during the fall 
season, while rigid pavements often 


64 


retain two-thirds of their fall strength. 
Linell attributed the greater strength 
retention of rigid pavements to their 
lesser dependency on the subgrade for 
support. 


Small scale laboratory strength tests 
have been conducted on undisturbed 
samples of the subgrade and on 
samples remolded to duplicate the 
subgrade moisture and density 
conditions found under weakened 
pavements. These tests confirm both 
the large changes in strength which 
occur as aresult of small changes in 
moisture and density, and those large 
changes in strength that occur during 
ice-melting. 


Although increased deflection is well 
documented, few corollary studies of 
actual pavement performance in 
terms of roughness and cracking 
associated with seasonal strength loss 
have been made. Recent promising 
developments in dynamic methods for 
rating pavements, such as the Road 
Rater and the Dynaflect* have had 
only limited application in the study 
of seasonal strength of pavements. 
The most comprehensive study using 
dynamic methods to evaluate frost 
effects on the seasonal strength of 
pavements was conducted in Illinois 
and Minnesota during the winter of 
1968-69. Conclusions from this study 
indicated that the Dynaflect was 
better suited for detecting seasonal 
changes than the Benkleman Beam, 
plate bearing, and a curvature meter 
test (8). 


It should be anticipated that with 
dynamic devices much more can be 
learned in the future about the 
seasonal and daily changes in the 
strength of pavement systems. There is 
very little literature on critical strength 
condition measurements over 24-hour 
periods. 


3The United States Government does not 
endorse products or manufacturers. Trade or 
manufacturers’ names appear herein solely 
because they are considered essential to the 
object of this report 


September 1974 @ PUBLIC ROADS 





METHODS FOR MINIMIZING 
SEASONAL CHANGES IN 
PAVEMENT STRENGTH DUE TO 
FROST ACTION 


Where existing roads are weakened by 
spring thaw and reconstruction funds 
are limited, some States reduce the 
maximum allowable axle load during 
the thaw period. Because this 
restriction is difficult to enforce, many 
States have strengthened their 
pavements on major routes so that no 
restriction is needed. However, 
strengthening existing pavements 
results in over-strength pavements for 
a large part of the year. As aresult,a 
large part of the additional investment 
is used only during the spring thaw. 


It is usually more economical to 
design and construct pavements 
initially so that seasonal strength 
changes are minimized. Methods used 
to date include: 


@ Insulation of the subgrade. 


m Chemical additives to reduce frost 
susceptibility. 


m Excavation of frost susceptible 
materials and replacement with non- 
frost susceptible materials. 


= Control of water through drainage. 
Insulation of the subgrade 


Studies have shown that granular 
materials are poorer insulators than 
other soil-aggregate materials (9). In 
experimental installations designed to 
insulate frost susceptible subgrades, 
many States have placed layers of 
expanded plastic foam between the 
subgrade and overlying granular layers 
of subbase. Where drainage is 
adequate, the plastic foam is effective 
in limiting frost penetration. For 
example, during the winter in Ontario, 
Canada, with a freezing index of 2,600 
degree days, 2 inches (50.8 mm) of 
foamed plastic reduced frost 
penetration from 5.41 ft (1.65 m) in 
uninsulated conditions to only 2.5 ft 


PUBLIC ROADS e Vol. 38, No. 2 


Table 1.— Evaluation of additives as frost modifiers! 





Additive Required | 


Cost 


Evaluation as 





sett st ccsel 


per pound [ 


| Field use 


per kg frost modifier 





Percent Dollars 
Void pluggers and cement 
in situ polymerization >5 
(calcium acrylate) 


> 0.50 


Dollars 


Difficult to con- 
trol polymeri- 
zation 


> 0.23 





Resins 0.01—0.15 





Portland cement 20.01—0.02 
30. 06—0.12 


0.00—0.02 





Natural fines 


Aggregants 


Polymers 0.12— 1.00 





0.004—0.07. Other than cure 
requirements, 
no special 
problems 
0.004—0.01 No special prob- Interesting to 
0.03—0.05 lems oor 
0.00—0.01 Probably unusual Interesting 
mixing and 
processing 
problems. 


Promising 


0.05—0.45 Moderate mixing Interesting to 
and processing poor 
problems ex- 


pected 





Cations 0.02 and up 


Dispersants 0.05— 1.00 


Waterproofers 0.25—2.00 


TAfter Lambe (117) 
2Cement 
3Additives 





(0.76 m) under the insulated areas 
(10). Use of the foam required special 
placement techniques and an 
overlying depth of material for the 
pressure distribution of construction 
and design wheel loads. Deflection of 
the foam-insulated pavement system 
is anywhere from 0.25 to 0.5 in. (6.4 to 
12.7 mm) greater than deflection of an 
untreated area. Also, the plastic 
should extend outside the pavement 
to protect the edges of the pavement 
from heat loss through the shoulders. 


Icing of pavements over insulated 
subgrades has occasionally been a 
safety problem. Very recently, 
manufacturers of some proprietary 
insulation materials in the United 
States have requested a waiver of 
liability from the State highway 
departments for any claims that might 
result from the use of their product. 
Since some accidents have occurred 
because of icing of the surface under 
certain moisture and temperature 
conditions, some of the States have 


65 


0.01andup No special prob- Very 


lems expected promising 
0.02—0.45 No special prob- Do 
lems. 
0.12—0.90 Need for high 
degree of drying. 


Promising 


suddenly become very reluctant to 
incorporate these proprietary 
materials for insulation purposes. 


Chemical additives to reduce frost 
susceptibility of soils 


Extensive laboratory and limited field 
experience have shown chemical 
additives to be effective in reducing 
the frost susceptibility of subgrade 
soils (11). Additives can usually be 
classified into one of four different 
types: (1) Void fillers and cements, 

(2) aggregants, (3) dispersants, and 
(4) waterproofers, according to their 
action on the soil. The most promising 
are resins, cation aggregants, 
dispersants, and waterproofers, as 
shown in table 1. Well-graded soils 
respond best to treatment, making the 
use of additives attractive for 
modifying dirty gravels, sandy clays, 
and silty sands. Uniform silts and 
plastic clays were the least responsive. 
As with all soil modifiers, obtaining a 


uniform mixture of modifier with the 
soil can present problems, especially 
when the soil is a wet clay. 


Excavation and replacement of frost 
susceptible materials 


Although granular materials are not 
particularly good insulators, 
replacement of frost susceptible 
material with clean, granular backfill 
is the most popular and usually most 
successful method for reducing both 
heaving and loss of strength during the 
thawing period. The method reduces 
both overall heave and differential 
heave, and, if drainage is adequate, 
results in retention of strength. 
Replacement is generally to a depth of 
from 50 to 100 percent of the depth of 
frost penetration. On high type roads 
where granular materials are plentiful, 
replacement is often to 100 percent of 
frost penetration. The granular 
material is apparently effective 
because it reduces the supply of 
capillary water to the frost zone and 
permits better drainage of surface 
water entering the pavement system. 
In areas of high precipitation, and in 
areas with either ground-water 
seepage problems or a high water 
table, it is therefore important when 
specifying frost free materials to 
require a low percentage of material 
finer than 0.001 in. (0.02 mm), and to 
require no more than 0.04 in. (1.0 mm) 
heave per day when the soil is 
subjected to a laboratory frost 
susceptibility test proposed by the 
U.S. Army Corps of Engineers (CREEL) 
(12). According to CREEL, to control 
frost heave, the amount of material 
finer than 0.001 in. (0.02 mm) should 
be no more than 1 1/2 to 3 percent for 
granular, well-graded sands and silty 
sands, and no more than 10 percent 
for uniform sandy soils. 


Research on criteria for frost 
susceptibility is being studied further 
by the Pennsylvania, Massachusetts, 
and New Hampshire highway 
departments under current projects 
sponsored by the FHWA. 


Control of the water supply through 
drainage measures 


Methods to reduce frost action 
through control of temperature 
(insulation), modification of frost 
susceptible soils, and replacement of 
frost susceptible soils are effective 
only when adequate drainage is 
assured to minimize movement of 
water into the frost zone and to drain 
melt-water from above the frozen 
zone. In many problem cases, good 
drainage alone will result in a high 
percentage of retained bearing 
capacity during the spring thaw. The 
following special drainage measures 
are effective: 


m Drain open-graded layers. 


w Drain water trapped in ledge (rock) 
cuts. 


m Provide deep side ditches to help 
lower the water table. 


m Drain seepage layers, especially 
those which are exposed when the 
roadway is perpendicular to contours. 


m Provide drainage for seepage 
layers under side hill fills. 


wm Place underdrains in shaded areas 
where frost penetration is deeper. 


gw Drain low points of subbase 
materials. 


m Raise the pavement grade in high 
water table areas. 


m Place underdrains in wet cuts 
unless the soil is pure silt or clay, in 
which case, undercut and backfill. 


The major problem in designing 
drainage for pavements in cold areas 
is keeping the drainage system from 
being blocked by ice. Pipe outlets 
placed low in side ditches often 
remain frozen when melt-water under 
the pavement needs an outlet. 
Wherever possible, outlets should be 
placed in the side of the embankment 
at least 1 ft (305 mm) above the ditch 
invert. Gate flaps on pipe outlets may 
delay ice blockage by keeping cold air 
out of the pipe. 


66 


Differential heaving over shallow | 
drains has been a problem in some 

States. This is generally attributed to 

the cold-air chimney effect in the 

pipe. Placement of small pipes at least 

2 ft (610 mm) below the pavement 

surface reduces the differential 

heaving. 


Because of the sequence of freezing 
from above and then thawing from 
above and below, drainage problems 
are created by the block of ice left 
between the lower and upper thawed 
zones. In climatic areas where the 
frost penetration is deep and ground 
water seepage is a problem, it is the 
author's opinion that a two-layer 
drainage system is needed in the 
roadway. One layer should be placed 
below the deepest frost penetration to 
drain ground water seepage, reducing 
both free water and capillary water. 
Another layer should be placed high in 
the pavement system to drain water 
from thawing ice in the upper layers of 
the pavement during warm spring 
days. This top drainage layer could 
consist of an asphalt-treated, open- 
graded drainage layer as part of the 
pavement structure, as advocated ina 
report recently prepared for the FHWA 
under an administrative contract (73). 
A distinctive feature of this system is 
the high permeability of the open- 
graded layer—0O.12 to 0.28 in./s (0.003 
to 0.007 m/s)—and the use, where 
necessary to prevent intrusion, of a 
filter layer of sand or fibrous material 
both above and below the open- 
graded layer. This graded filter 
drainage system has been quite 
successful in draining ground water 
seepage in warm, high rainfall areas of 
California. One of the installations has 
been placed in a colder climate and its 
performance is under observation.4 
When this type of shallow drainage is 
placed in very cold areas, particular 
attention should be paid to parts of 
the drainage system which might 


4EHWA HP&R Research Project, California D-2- 
1,Open Graded Asphalt Treated Drainage 

Blanket,” California Department of 

Transportation, Sacramento, Calif 


September 1974 e PUBLIC ROADS 





LINES OF PROGRESSIVE THAWING 


INSULATED OUTLET PIPE 


61444144 EI ET 


Figure 4.—Possible solution 
to ice blockage 
of shallow drains. 


remain frozen while that part under 
the pavement thaws. For example, ice 
in outlet pipes under the shoulder will 
probably thaw last because of snow 
cover on the shoulder or less heat- 
absorbing surfacing material. This ice 
could temporarily block the drainage 
of melted ice water under the 
pavement. Although it is not covered 
in the FHWA report “Guidelines for 
the Design of Subsurface Drainage 
Systems for Highway Structural 
Sections” (13), it is the author’s 
opinion that the problem of ice 
blockage in cold sections of the 
drainage system can be alleviated 
through the use of pipes made of a 
high heat conducting material and 
surrounded by a good insulator (fig. 4) 
in those areas remaining frozen the 
longest. This type of construction 
could provide sufficient heat flow 
from the warm areas under the 
pavement to the cold areas under the 
shoulder and maintain an open 
drainage system during the critical 
thaw period. Typical gradations and 
permeabilities of the open-graded 


~ drainage layer and granular filter 


materials for the layered drainage 
system are shown in figure 5. This type 
of pavement drainage will also handle 
infiltration of rain and melted snow 
from the surface during warm weather 
(73). 


PUBLIC ROADS e Vol. 38, No. 2 


Ck 


50 30 2016 108 


U.S. STANDARD SIEVE SIZES 


Figure 5.— Typical gradations and 
permeabilities of open-graded bases 
and filter materials (13). 


67 


GATE FLAP 


Y 


1 FT=0.305 m 





TOTAL PERCENT PASSING 





SUMMARY 


The supporting strength of pavements 
is constantly fluctuating as a result of 
environmental influences. In cold 
climates, the critical strength period 
occurs during the spring thaw. 
Pavement structures must be designed 
to support heavy wheel loads during 
their weakest period or the change in 
subgrade and pavement strength must 
be minimized by either modifying or 
replacing frost susceptible materials 
and, above all, by assuring adequate 
drainage of both the subgrade and the 
pavement structure. 





REFERENCES 


(1)  S. Taber, “Frost Heaving,” Journal of 
Geology, vol. 37, 1929, pp. 428-461. 


(2) _E.S. Barber and G. P. Steffens, “Pore 
Pressures in Base Courses,” Proceedings, 
Highway Research Board, 1958. 


(3) C.J. Van Til, et al., “Evaluation of AASHO 
Interim Guides for Design of Pavement 
Structures,” NCHRP Report 128, Highway 
Research Board, 1972. 


(4) “Pavement Research,” The AASHO Road 
Test, Report 5, Special Report 61E, Highway 
Research Board, 1962. 


(5) J. F. Shook and H. Y. Fang, “Cooperative 
Materials Testing Program at the AASHO Road 
Test,” Special Report 66, Highway Research 
Board, 1961. 


(6) “Report of Committee on the Load- 
Carrying Capacity of Roads as Affected by Frost 
Action,” Bulletin 96, Highway Research Board, 
1955. 


(7) K.A.Linell and J. F. Haley, “Investigation 
of the Effect of Frost Action on Pavement 
Supporting Capacity,” Special Report No. 2, 
“Frost Action in Soils,” Highway Research Board, 
1952. 


(8) F.H. Scrivner, R. Peohl, W. M. Moore, and 
M. B. Phillips, “Detecting Seasonal Changes in 
Load-Carrying Capabilities,” NCHRP Report 76, 
Highway Research Board, 1969. 


(9) “The WASHO Road Test,” Special Report 
22, Part 2,’’Test Data, Analyses, Findings,” 
Highway Research Board, 1955. 


(10) E. Penner, M. D. Oosterbaan, and R. W. 
Rodman, “Performance of City Pavement 
Structures Containing Foamed Plastic 
Insulation,” Record 128, Highway Research 
Board, 1966. 


(11) T.W. Lambe, “Modification of Frost 
Heaving Soils with Additives,” Bulletin 135, 
Highway Research Board, 1956. 


(12) K.A. Linell and C. W. Kaplar, “The Factor 
of Soil and Material Type in Frost Action,” 
Bulletin 225, Highway Research Board, 1959. 


(13) H.A. Cedergren, J. A. Arman, and K. H. 
O’Brien, “Guidelines for the Design of 
Subsurface Drainage Systems for Highway 
Structural Sections,” Federal Highway 
Administration, Washington, D.C., 1972, 
available (by stock No. PB 220116) from the 
National Technical Information Service, 5285 
Port Royal Road, Springfield, Va. 22151. 


PRICE INCREASE FOR PUBLIC ROADS 


Effective with the March 1974 issue, the annual domestic subscription rate 
for Public Roads was increased to $6.10 ($1.55 additional for foreign 
mailing). The price increase is attributed to an increase in the number of 
pages and additional color, as well as rising printing, labor, and paper costs 


and new postal rates for 1974. 


The Federal Highway Administration produces the magazine. The 
Superintendent of Documents, U.S. Government Printing Office, 
establishes subscription rates and conditions of sale. 


68 





September 1974 e PUBLIC ROADS 





The Bridge Rating and Analysis 
Structural System (BRASS) is a set of 
45 computer programs with 
documentation designed to aid in the 
long range structure inventory and 
appraisal of bridges along the Nation’s 
highways. The present 45 programs 
evolved from a series of bridge design 
and analysis programs developed by 
the Wyoming Highway Department 
during 1967-1972. Structural review 
and load rating capabilities were 
added to the bridge design and 
analysis programs to form the bridge 
rating system. This additional work 
was sponsored by the Implementation 
Division, Office of Development, 
Federal Highway Administration 
(FHWA), through one of its 
administrative contracts. 


PUBLIC ROADS e Vol. 38, No. 2 


NN SPD 


by Richard L. Sharp 
and Webster H. Collins 


The BRASS programs are written in the 
FORTRAN IV computer programing 
language and were developed on an 
IBM 360 Model 40 computer. ! With a 
minimal data requirement, the 
system’s programs assist in the 
analysis of the loading and structural 
characteristics of a highway bridge, 
furnishing aggregate and detailed 
estimates of dead load and live load 
stresses and a rated level of structural 
service (fig.1). The programs are easily 


IThe United States Government does not 
endorse products or manufacturers. Trade or 
manufacturers’ names appear herein solely 
because they are considered essential to the 
object of this report 


69 


executed and not constrained by the 
characteristics of their host computer, 
are flexible and user oriented, adhere 
to uniform bridge design standards, 
and will work for any State highway 
organization. Complete 
documentation of the programs, 
including example problems and 
program diagnostic aids, is available 
to the rating system user from the U.S. 
Department of Transportation, Federal 
Highway Administration (HNG-30), 
Washington, D.C. 20590. 


Figure 1.—BRASS in use. 








Capabilities exist in the system for 
designing, reviewing, and load rating a 
wide variety of highway bridges. The 
system will accommodate the 
following types of bridges (both 
simple span and continuous): Timber, 
welded steel plate, composite welded 
steel plate, rolled steel beam, compos- 
ite concrete-steel beam, steel I|-beam 
(both welded and riveted), cast- 
in-place concrete slab, concrete 
T-beam, concrete box girders, con- 
crete box culverts, concrete and steel 
rigid frame structures including slant 
leg structures, and hybrid girders (figs. 
2-5). It will accommodate up to 18 
continuous spans. The system will 
handle vehicles with any selected axle 
spacings and axle loads. It can handle 
vehicles with varying numbers of 
axles —up to a maximum of 24 axles. 
In addition, the system accommodates 
the standard AASHTO type loads. For 
these loads, it automatically handles 
the variable axle spacing and provides 
maximum live load moments at 
critical points. 


Between February and April 1973, the 
Office of Development sponsored 
training workshops on the bridge 
rating system. These workshops were 
conducted jointly by personnel from 
the Wyoming Highway Department 
and FHWA’s Region 8 and Wyoming 
Division Offices. These training 
workshops were designed to assist 
FHWA and State highway bridge 
engineering personnel in the use of 
the programs. Five separate workshops 
were held across the Nation in which 
more than 150 bridge engineers were 
trained in the use of the system. 


Immediately after the workshops, 25 
State highway agencies requested 
copies of the BRASS programs. In 
response to their requests, a magnetic 
computer tape was sent by Wyoming 
to each State. This tape contained the 
FORTRAN IV source code statements 
for the 45 programs as developed for 
the IBM 360 computer under the disk 
operating system (DOS). 


After receiving the initial tape 
containing the BRASS programs, many 
States requested the rating system be 
converted to run on the IBM 360 
computer under the full operating 
system (OS). Accordingly, the 
Implementation Division requested 
FHWA’s Computer Services Division 
to convert the rating system from DOS 
to OS. This conversion was 
accomplished from June through 
September 1973. Following this 
conversion, some revisions and certain 
improvements to the system were 
made during October by the Wyoming 
Highway Department. These revisions 
and improvements were forwarded to 
FHWA’‘s Computer Services Division 
who made a second conversion of the 
system from DOS to OS. Wyoming 
sent a single magnetic tape of this new 
version of the bridge rating system to 
the 25 State highway agencies having 
already requested BRASS. This 
distribution of the modified system 
was accomplished by December 1, 
1973: 


Further testing will be done by the 
States using the latest version of the 
system. This additional testing will 
undoubtedly raise questions 
concerning either program results or 
OS problems and these will have to be 
resolved. Also, since this system is new 
and complex, it is expected that users 
will discover problems in the system 


70 





sos labia se 


Figure 2.—Analysis and rating of cast- 
in-place and prestressed concrete 
bridges are in the system’s scope. 


and will require assistance. Corrective 
measures and answers to user 
problems must be developed by one 
who is thoroughly familiar with the 
internal features of the system. 
Accordingly, the Implementation 
Division is sponsoring a contract to 
provide a maintenance service 
whereby users may contact a 
contractor for help with problems 
discovered in the system. The 
Wyoming Highway Department — 
developer of the system — is serving as 
the maintenance contractor. At the 
end of this contract maintenance 
service, FHWA’s Bridge Division, 
Office of Engineering, will provide any 
future service which may become 
necessary. 


As mentioned earlier, the bridge rating 
system may be obtained from FHWA‘s 
Bridge Division on request. In 
response to such requests a BRASS 
Implementation Package will be sent. 
This package contains complete 
documentation and a single magnetic 
tape, on which are the FORTRAN IV 
source code statements for the 45 


September 1974 e PUBLIC ROADS 


OE agencies 





programs. The documentation 
includes the BRASS Reference Manual 
which details the coding of bridge 
structural and loading data for 
processing and also contains test data 
which allow the recipient to 
implement and execute BRASS 
without extensive collecting or coding 
of data. These test data provide output 
examples and serve a tutorial 
function. 


Instructions on how to install the 
bridge rating system on a local |BM 
360 computer will be sent with the 
implementation package. Any agency 
receiving BRASS will be kept informed 
regarding its use, modification, and 
improvements. 


PUBLIC ROADS e Vol. 38, No. 2 


fee ¢ t 


s Picicna, : 
ear ea se gil gen tk Gone 
i ee ae ee Eee 


Pie peer € 
ee te Bee ee he kT 


Figure 3.—BRASS may be used to 
check design calculations and to rate 
new bridges. 


Figure 4.— BRASS analyzes and rates 
bridges with rolled and fabricated 
members. 


Figure 5.— The system calculates 
section properties for damaged 
members. 


71 












The new design technique described 
in this article was developed by the 
Office of Research, Federal Highway 
Administration (FHWA), and is offered 
as a logical approach to the design of 
open-graded asphalt friction overlays. 
It provides a means to overcome with 
reasonable assurance some of the past 
difficulties encountered in design, 
construction, and field performance. 
The overall simplicity of the 
methodology and the low capital 
investment in required laboratory 
equipment contributes to its 
suitability for acceptance ona 
national level. 


The described method has been used 
successfully on several FHWA Region 
15 demonstration projects. It is 
believed that the method provides 
technological improvements over 
other existing methods, and its use is 
recommended for immediate 
experimental application. Assistance 
and instruction in the use of the 
procedure are available to interested 
agencies through the FHWA Region 
15 Demonstration Project 10. 


Design of Open-Graded 
Asphalt Friction Courses 


by! Richard W. Smith, James M. Rice, 
and Stewart R. Spelman 


INTRODUCTION 


Most of the highway community is 
familiar with the type of overlay 
commonly referred to as an open- 
graded plant mix seal coat. According 
to most available reports, this type of 
surfacing evolved from the 
conventional chip seal surface 
treatment which is used primarily to 
seal and maintain aged, but otherwise 
structurally sound, pavements. It is 
what its name implies —a chip seal 
aggregate mixed hot ina plant witha 
relatively high percentage of asphalt 
cement and placed to a compacted 
depth of 5/8 to 3/4 of an inch (16 to 19 
mm) by an asphalt paver. The history 
and extent of plant mix seal usage has 
been adequately discussed and 
documented in the literature (1-8). 
Some of the benefits which have been 
associated with the use of plant mix 
seals are: 


= Improved skid resistance at high 
speeds during wet weather. 


= Minimization of hydroplaning 
effects during wet weather. 


= Improved road smoothness. 


= Minimization of splash and spray 
during wet weather. 


= Minimization of wheel path 
rutting. 


\ This article is an abridgment of “Design of 


Open-Graded Asphalt Friction Courses,” by R.W. 


Smith, J.M. Rice, and S.R. Spelman, which is 
available from the National Technical 
Information Service, 5285 Port Royal Road, 
Springfield, Va. 22151, PB No. 227479 


2\talic numbers in parentheses identify the 
references on page77 


72 


= Improved visibility of painted 
traffic markings. 


S Improved night visibility during 
wet weather (less glare). 


™ Lower highway noise levels. 


B® Retardation of ice formation on 
surface. 


In spite of these benefits, the use of 
plant mix seals has not been very 
extensive because of a number of 
uncertainties and problems involved 
in their design and construction. The 
FHWA has recently initiated an all-out 
effort to overcome the problems 
which prevent the motoring public 
from receiving the benefits associated 
with this type of surfacing material. 


THE PROBLEM 


The greatest discernible difficulty in 
this effort was that current design 
practice was not well defined. In most 
instances, the only design criteria 
available were limits on the aggregate 
gradation and ranges of values for 
asphalt content which were based 
primarily on field experience. Existing 
methods of design seemed to rely 
either on surface treatment concepts 
or on the application of routine design 
methods that are generally only 
suitable for dense, cohesive type 
mixtures. The open-graded plant mix 
seal, however, does not fit into either 
category. 


September 1974 e PUBLIC ROADS 


t 











OPEN-GRADED ASPHALT FRICTION COURSE CORRECTS 
POOR NIGHT VISIBILITY DURING RAINY WEATHER 


The main design consideration that 
created problems appeared to be the 
determination of the percentage of 
asphalt cement to be used. The 
amount was usually selected by 
conducting a series of asphalt 
drainage tests on trial mixtures at 
various percentages of asphalt. The 
basis for this design approach was 
simply the requirement that a 
sufficient quantity of asphalt cement 
be made available for the formation of 
a seal on the existing road surface, but 
not so much as to Cause excess 
drainage, segregation, or handling 
problems during construction. The 
undesirable aspect of selecting asphalt 
content in this manner is that the 
drainage test temperature is made the 
controlling factor rather than, more 
properly, the inherent properties of 
the material constituents or of the 
resulting mixture. 


When asphalt content was selected by 
the use of more advanced equipment, 
such as the Marshall or Hveem 
apparatus, it was found that stability 
-and flow were quite insensitive to 
variations in asphalt percentage. 
Selecting the asphalt content on the 
basis of optimizing stability and flow 
did not provide definitive results. 


The selection of asphalt content by 
either drainage tests or mechanical 
tests requires considerable 
engineering judgment. Using either of 
these methods, it is quite possible for 
the mixture to contain too little 


PUBLIC ROADS e Vol. 38, No. 2 


asphalt, which would create a raveling 
condition, or too much asphalt, which 
would create a flushing condition. 


A DIFFERENT APPROACH 


In the course of our analysis of the 
problem, it became evident that 
highway engineers have been using 
open-graded plant mix seals for two 
distinct purposes: (1) Maintenance of 
aged and weathered pavement 
surfaces, and (2) specifically forthe 
improvement of pavement friction. 
Since the latter purpose is the primary 
concern of the FHWA, we thought it 
desirable to advance the open-graded 
plant mix seal still further, into the 
open-graded asphalt friction course. 
Referring to the previous discussion, 
an open-graded asphalt friction course 
might best be considered a plant mix 
seal without the excess asphalt 
cement which forms the seal. 


Although this distinction may seem 
relatively minor, it does greatly reduce 
the difficulty that is encountered in 
mixture design and pavement 
construction. Using this concept, a 
more definite design procedure can be 
established without sacrificing any of 
the benefits. It is still important, 
however, to provide a watertight seal 
at the interface with the existing 
pavement system to prevent water 
infiltration. It is recommended that 
the existing surface be treated 
separately from the new surfacing 
material with a tack coat. If the 


73 


existing surface is porous and dry, a 
prime coat should be applied. If it is 
flushed, the excess asphalt should be 
removed. 


The design procedure, then, is based 
on the concept that the open-graded 
asphalt friction course consists 
predominantly of a narrowly-graded 
coarse aggregate fraction—defined 
here as the material that is retained on 
a No. 8 (2.36 mm) sieve—with a 
sufficiently high interstitial void 
capacity to provide for a relatively 
high asphalt content, a high air void 
content, and a small fraction of fine 
aggregate—defined as that material 
passing a No. 8 (2.36 mm) sieve. The 
coarse aggregate fraction provides the 
structure of the composite mixture 
while the fine aggregate fraction acts 
primarily as a filler within the 
interstitial voids and as a stabilizer for 
the coarse aggregate fraction. 


Material requirements 


The highway community is now 
cognizant that pavement skid 
resistance is not only a function 

of the larger scale texture or macro- 
texture, but also of the small 

scale texture or microtexture which 
can barely be felt by touch. Ina 
typically dense-graded asphalt 
mixture, the pavement macrotexture Is 
provided by the coarse aggregate, 
while the microtexture can be 
provided by both the coarse and fine 
aggregates. In the open-graded asphalt 





friction course, however, the coarse 
aggregate fraction must provide the 
necessary microtexture without 
assistance from the fine aggregate. For 
this reason, it is very important that 
this be considered when selecting the 
coarse aggregate. A number of 
aggregates derive their excellent 
microtexture properties through the 
process of attrition, but in some cases 
this can be excessive in terms of 
abrasion loss requirements. A 
compromise might, therefore, be 
required between friction and 
abrasion properties. 


It is recommended that relatively pure 
carbonate aggregates or any 
aggregates known to polish be 
excluded from the coarse aggregate 
fraction—material retained on No. 8 
(2.36 mm) sieve. In addition, the 
coarse aggregate fraction should have 
at least 75 percent by weight of 
particles with at least two fractured 
faces and 90 percent with one or more 
fractured faces. The abrasion loss 
(AASHTO T 96) should not exceed 40 
percent. 


The attainment of the required 
drainage and macrotexture properties 
(see fig. 1) is more or less implicit with 
adherence to the following 
recommended limits on the aggregate 
gradation which have been borrowed 
largely from field experience (9): 


U.S. sieve size Percent passing 


3/8 inch 

(9.5 mm) 100 
No. 4 3050 
(4.75 mm) 
No. 8 515 
(2.36 mm) 

No. 200 25 
(75 um) 


Limits which are given for the No. 8 
(2.36 mm) sieve are intended primarily 
as a guide. The overriding 
consideration which actually dictates 
the maximum limit is that all material 
finer than this limit must fit within the 
interstitial voids of the composite 
forming material—that retained on 


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Figure 1.—Functional concept of open-graded asphalt friction 


GOUTLS G2 


No. 8 (2.36 mm) sieve. The uniformity 
of the aggregate grading between the 
No. 8 (2.36 mm) sieve and the No. 200 
(75 pm) sieve is an important factor 
affecting the quantity that can be 
used, as are the shape characteristics 
(roundness and sphericity) of the 
coarse aggregate fraction. The 
importance of including at least some 
fine-sized aggregate cannot be 
overemphasized, as its primary 
purpose is to provide a chocking 
action for the stabilization of the 
coarse aggregate fraction. 
Consequently, minimum requirements 
have been provided. Limits which are 
given for mineral dust—passing 

No. 200 (75 um) sieve —help to assure 
some degree of uniform grading of the 
fine aggregate, as well as to control 


74 


the asphalt drainage characteristics of 
the mixture by effectively increasing 
the viscosity of the asphalt cement. 


The suggested grade of asphalt 
cement to be used is AC-10 or AR-40 of 
AASHTO M226-731. These grades 
should be considered a tentative 
starting point because test results 
obtained from the design process may 
indicate an advantage or anecessity 
to alter the asphalt grade. 


Asphalt content 


The method of selecting the asphalt 
content consists of two steps. The first 
is to conduct a measurement of the 
surface capacity (Kc) of the 
predominant aggregate size fraction— 


September 1974 e PUBLIC ROADS 





material retained on No. 4 (4.75 mm) 
sieve. Surface capacity includes 
absorption, superficial area, and 
surface roughness —all of which affect 
asphalt cement requirements (10). 


The second step is to compute the 
required asphalt content from an 
established simple linear relationship 
obtained from field experience on 
similar mixtures (5): 


Percent asphalt =*2.0(Kc) + 4.0 


Asphalt content so determined is 
based on weight of total aggregate. A 
basic difference between this design 
procedure and its predecessors is that 
this value for asphalt content is to be 
considered final in that no further 
adjustments are to be made based on 
asphalt drainage characteristics, 
stability, or any other criteria. 
However, after the subject report had 
been distributed, a refinement for 
asphalt content was found necessary 
for mixtures containing certain types 
of aggregates such as expanded clays 
and shales. Although the original 
formula undoubtedly accounted for 
small variations in aggregate specific 
gravity because it was based on field 
experience, it cannot be used for 
mixtures in which the apparent 
specific gravity of the aggregate is 
markedly different from 2.65. 
Therefore, it is suggested that a 
corrected asphalt content be 
calculated by the formula: 


Corrected percent asphalt 


percent asphalt x 2.65 
apparent specific gravity of aggregate 


The corrections will be relatively 


insignificant for most aggregates other 
than the lightweight expanded clays or 


shales. 


30ther equations which have been used are: 
FOA=1.5 (Kc) + 3.5 and FOA= 1.5 (Kc)+ 4.0 by 
California and Colorado, respectively 


PUBLIC ROADS e Vol. 38, No. 2 


Void capacity of coarse aggregate 


A portion of the procedure covers the 
measurement of the interstitial void 
capacity of the coarse aggregate 
fraction—material retained on No. 8 
(2.36 mm) sieve —of the proposed 





Figure 2.—FHWA vibratory 
compaction apparatus (11). 


gradation. This information is 
obtained by conducting a vibratory 
unit weight determination (17). The 
desirable feature of this test is the high 
degree of densification achieved 
without causing a significant amount 
of aggregate degradation. This test 
provides an indication of the 
minimum level of interstitial voids 
that will exist in the coarse aggregate 
fraction of the friction course after 
long-term densification under high 
traffic volumes—assuming no 
aggregate degradation. In essence, the 
compactive characteristics of the 


75 


coarse aggregate fraction are 
determined not only by the gradation, 
but also by particle sphericity and 
roundness. The essential components 
of this test are illustrated in figure 2. 
The main element shown is an 
electromagnetic vibratory rammer 
with a frequency of 3,600 Hertz and a 
mass of 25 pounds (11.34 kg). 


Optimum content of fine aggregate 


The optimum content of the fine 
aggregate fraction is that amount 
which can fit within the interstitial 
voids of the coarse aggregate fraction, 
while at the same time allowing a 
sufficient portion of the interstitial 
voids for the asphalt cement and for a 
minimum quantity of air voids. The 
maximum quantity of fine aggregate is 
limited not only by absolute volume 
requirements, but also by the particle- 
size distribution of the fine aggregate 
(i.e., the fine aggregate has its own 
interstitial void system). An implied 
requirement of the design method is 
that the interstitial void system of the 
coarse aggregate fraction will not be 
made greater by the addition of the 
fine aggregate fraction. This insures an 
internal void system with large-sized 
voids for water drainage purposes. The 
assumption is made that the above 
requirement will be satisfied provided 
that the fine aggregate fraction is 
limited to a maximum of 15 percent by 
volume of the total aggregate (or by 
weight if the coarse and fine aggregate 
fractions are of the same specific 
gravity). 


A minimum air void content of 15 
percent is recommended for design 
purposes to insure adequate 
subsurface water drainage. It is this 
condition which gives the mixture its 
desirable features. Information 
supporting the criterion of 15 percent 
is scarce; however, it has been shown 
that for approximately the 
recommended aggregate grading 
(Marshall samples compacted at 50 
blows per side yielded air void 
contents of 15.6 percent) the resulting 


water infiltration capacity of the 
mixture when compacted toa 
pavement thickness of 1 in. (25.4 mm) 
proved to be sufficient (72). 


The fine aggregate content may be 
expressed in general terms by the 
following relationship on a percentage 
by volume basis: 


Fine aggregate passing No. 8 (2.36 
mm) sieve 


= Void capacity (VMA) retained 
No. 8 (2.36 mm) sieve 


— Design asphalt content 
— Design void content 


+ Asphalt absorption by 
aggregate 


The above expression has been 
translated into a quantitative 
mathematical equation and included 
as part of the design procedure. As an 
alternate to using the equation, a 
simplified nomograph (fig. 3) is also 
provided which is applicable for a 
wide range of materials. Neither the 
equation nor the nomograph includes 
a correction for asphalt absorption 
since it is assumed to be negligible in 
most Cases. 


Optimum mixing temperature 


The optimum mixing temperature Is 
based on the concept that the 
aggregate should be heated hot 
enough to be reasonably dry to 
facilitate coating and adhesion, yet 
not be so hot as to reduce the viscosity 
of the asphalt binder to a level which 
facilitates drainage and segregation of 
the asphalt from the aggregate during 
transit from the mixing plant to the job 
site. The recommended target mixing 
temperature is in the range that will 
corrrespond to asphalt cement 
viscosities of 700 to 900 centistokes. A 
simple test is provided in the 
procedure to investigate the drainage 
characteristics of the design mixture. 
This consists of maintaining asample 
of the mixture in a glass container at 
the mixing temperature for a 
prescribed period, and then observing 
for drainage. The purpose of this test is 


not to determine asphalt content as 
has been done in the past, but rather 
to determine the mixing temperature 
at which the recommended quantity 
of asphalt may be used. If asphalt 
drainage occurs at a mixing 
temperature which is too low to 
provide for adequate drying of the 
aggregate, an asphalt of a higher grade 
should be used (AC-20 or AR-80). 


Resistance to effects of water 


The accessibility of the interior of the 
open-graded asphalt friction course to 
water makes it important to 
investigate the tendency to lose 
strength in the presence of moisture. 
The criterion of strength is not 
believed to be as important as the 
criterion of retained strength. 


The Immersion-Compression Test 
(AASHTO T 165 and T 167) is required 


Figure 3.— Determination of optimum 
fine aggregate content. 


OF FINE AGGREGATE 


OF FINE AGGREGATE 


| 
Ww 
<= 
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WW 
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4 
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PASSING NO. 8 (2.36 mm) SIEVE 


0 
25 30 


UPPER SPECIFICATION LIMIT 


LOWER SPECIFICATION LIMIT 


for this investigation. A molding 
pressure of 2,000 psi (13.79 MPa) is 
used rather than the specified value of 
3,000 psi (20.68 MPa) to eliminate 
most aggregate degradation during 
compaction. Accordingly, the index of 
retained strength is specified as a 50- 
percent minimum — as contrasted to a 
70-percent minimum for dense-graded 
mixtures molded at 3,000 psi (20.68 
MPa)—after a 4-day immersion in 
120° F (48.899 C) water. Additives 
may be used to promote adhesion and 
to provide adequate retained strength. 


EXTENT OF USAGE 


The procedure which has been 
outlined is relatively new. However, in 
the course of conducting an initial 
investigation, it was possible to apply 
the procedure to the design of plant 
mix seals which were recently 


PERCENT OF ASPHALT 
CONTENT, BY TOTAL 
AGGREGATE = 2(Kc)+ 4.0 


EXAMPLE: IF VMA OF COARSE 
AGGREGATE IS 35 AND 
ASPHALT CONTENTIS 

6.5, THEN FINE AGGREGATE 
CONTENT WILL BE 10.4FOR 

A 15 PERCENT AIR 

VOID CONTENT. 


35 40 45 


VOIDS (VMA) IN COARSE AGGREGATE—PERCENT RETAINED 


NO. 8 (2.36 mm) SIEVE 


ASSUMPTIONS USED IN DERIVING CHART: 

SPECIFIC GRAVITIES OF COARSE AND FINE AGGREGATES = 2.65. 
SPECIFIC GRAVITY OF ASPHALT = 1.00. 

AIR VOID CONTENT= 15.0 PERCENT. 





76 


September 1974 e PUBLIC ROADS 





constructed under the auspices of the 
FHWA Region 15 Demonstration 
Project 10, in the States of New 
Hampshire, Minnesota, Michigan, 
New York, and Kentucky. These after- 
the-fact designs compared quite well 
with the designs recommended by 
FHWA Region 15 personnel, which 
were based on the Colorado procedure 
(8). A comparison of aggregate 
gradation and asphalt content results 
and a more complete listing of 
pertinent information obtained by this 
procedure are provided in the subject 
report. In the Kentucky and the New 
York designs, some 3/8- to 1/2-in. 
(9.5- to 12.7-mm) material was 
permitted. It is believed that a 
relatively small quantity of this size in 
the range of 5-10 percent will not 
significantly affect the desired mixture 
properties and is therefore allowable. 
This provision would permit the more 
economical use of standard sizes of 
aggregates. 


As aresult of the favorable 
comparison, the procedure was 
applied to the design of mixes fora 
demonstration project in Mississippi. 
This turned out to be especially 
challenging as three separate job-mix 
designs were requested, each 
containing various combinations of 
aggregate—crushed gravel, expanded 
clay (synthetic aggregate), and slag 
(phosphate type). These mixture 
designs were successfully placed in 
October 1973. Although it is too early 
to draw any conclusions regarding 
performance, it has been reported that 
all three sections are maintaining 
good skid numbers, excellent drainage 
qualities, and very satisfactory riding 
qualities .4 


Since the Mississippi project, a 
number of interested agencies have 
requested assistance and instruction 
in the use of this procedure through 
the FHWA Region 15 Demonstration 
Project 10. As a consequence, other 
successful demonstrations using 


mixtures designed by this procedure 
4 Paper by T.C. Paul Teng “Research and 
Evaluation of Hot Bituminous Plant Mix Seal 


Course,” Mississippi Asphalt Paving Seminar, 
April 1974. 


PUBLIC ROADS e Vol. 38, No. 2 


have been completed in Ohio and 
lowa. Similar projects are being 
scheduled in Pennsylvania, Kansas, 
West Virginia, Delaware, Hawaii, 
Montana, and Washington. 


CONCLUSIONS 


The authors believe that the design 
procedure described in the preceding 
paragraphs is a substantial 
technological improvement over other 
existing methods used to design open- 
graded asphalt mixtures. This opinion- 
is based on several considerations. 


First is the simplification of the usual 
process required to select asphalt 
content. Although the value 
determined is still based largely on 
field experience, asphalt requirements 
are desirably dependent on the effects 
caused by different types of 
aggregates. Furthermore, the 
relationship used to compute asphalt 
content seems to provide for as high 
an asphalt content as used anywhere 
in practice. The use of this relatively 
large amount of asphalt is facilitated 
by requiring and providing for 
adjustments in mixing temperature 
and grade of asphalt cement, if 
necessary. 


Second is the provision for the 
investigation of the compaction 
characteristics of the coarse 
aggregate. This step verifies whether 
adequate space is available in the 
composite structure for the required 
amount of asphalt, air voids, anda 
sufficient but limited quantity of fine 
aggregate. Essentially, the properties 
and characteristics of the aggregate to’ 
be used dictate how the aggregate 
shall be graded (within limits) in order 
that the desired mixture 
characteristics are achieved. 


Third is the knowledge that the 
application of this procedure would 
have averted the use of a mix design 
that was responsible for arather 
extensive incidence of asphalt 
flushing of an open-graded plant mix 
seal coat placed in the Washington, 
D.C. area in 1969. Evaluation of the 
actual mix design by the proposed 


mA 


new procedure indicates that 
insufficient void space was available 
in the coarse aggregate for the 
quantities of fine aggregate and 
asphalt cement that were used. 
Further improvements in the 
procedure are contemplated as results 
of current research efforts become 
available. However, the procedure in 
its present form is recommended for 
immediate application. 


REFERENCES 


(1) William L. Eager, “Construction and 
Performance of Plant Mixed Seal Coats,” 
Proceedings, American Association of State 
Highway Officials, 1967, pp. 235-246. 


(2) Gordon A. McKenna, “Plant Mix Seal Coats 
Used in Region Seven (FHWA),” Federal 
Highway Administration, Office of Engineering, 
distributed by Circular Memorandum, May 1968. 


(3) W. R. Lovering, “Open-Graded Asphalt Mix— 
Pros and Cons,” Roads and Streets, December 
1961, p. 84. 


(4) Doyt Y. Bolling, “Open-Graded Plant Mix 
Surface Courses in the Washington (D.C.) Area,” 
Conference on Skid Resistant Surface Courses, 
Arlington, Va., Federal Highway Administration, 
Report No. FHWA-RDDP-10-1, July 1970. 


(5) Robert A. Bohman, “Open-Graded Plant Mix 
Seals,” Conference on Skid Resistant Surface 
Courses, Chicago Heights, III., Federal Highway 
Administration, Report No. FHWA-RDDP-10-2, 
September 1971. 


(6) John A. Mills, “A Skid Resistance Study in 
Four Western States,” Special Report 101, 
Highway Research Board, 1969, pp. 3-17. 


(7) Wade B. Betenson, “Plant-Mixed Seal Coats 
in Utah,” Asphalt Paving Technology 1972, The 
Association of Asphalt Paving Technologists, 
pp. 664-684. 


(8) B. A. Brakey, “Design, Construction, and 
Performance of Plant Mix Seals,” Proceedings, 
American Association of State Highway 
Officials, 1972, pp. 177-195. 


(9) “Open Graded Plant Mix Seals,” Federa! 
Highway Administration, Office of Engineering, 
distributed by Notice, May 1973, p. 13. 


(10) “Method of Test for Centrifuge Kerosene 
Equivalent Including K-Factor,” Test Method 
303-E, California Department of Transportation. 


(11) D. G. Fohs, J. R. Blystone, and P. C. Smith, 
“A Vibratory Compaction Test Method for 
Granular Materials,” Federal Highway 
Administration, Report No. FHWA-RD-7 2-43, 
November 1972, available through the National 
Technical Information Service, Springfield, Va., 
22151, PB No. 221008. 


(12) R. W. Smith, “Influence of Permeance on 
Asphalt Concrete Hardening,” The Pennsylvania 
State University, December 1971. 








Report on Accident Experience 
with Impact Attenuators 


—A Best Seller 


by John G. Viner and Charles M. Boyer 


The final report on “Accident 
Experience with Impact At- 
tenuation Devices” (1)! is Now 
available. The report examines 393 
accidents involving impact 
attenuators (also called crash 
cushions) which were reported in 
conjunction with the National 
Experimental and Evaluation Program 
Project No. NEEP-4, “Impact 
Attenuation Devices,” administered 
by the Federal Highway 
Administration’s Office of Highway 
Operations. An interim report on this 
study was published in the October 
1971 issue of Public Roads (2). 


Accident reports used in this study 
were received on the Fibco impact 
attenuator? the Hi-Dro Cushion, the 
Stee! Drum attenuator, the TOR- 
SHOK, the Dragnet, and the 
Vermiculite Concrete barrier. The data 
involved 188 locations, mostly at 
elevated gores. 


Some 68 of these accidents involving 
impact attenuators were judged likely 
to have resulted in death or serious 
injury had the attenuator not been 
present. In these 68 accidents, 5 
resulted in fatalities and 12 in injuries 
requiring hospitalization. Thus, in 75 
percent of these cases, accident 
severity was reduced from probable 
fatalities or hospitalizing injuries to 
accidents involving only minor injury 
or property damage. In these 68 major 
accidents, vehicle overturns occurred 
in Six Cases. 


Italic numbers in parentheses identify the 
references, 


2The United States Government does not 
endorse products or manufacturers. Trade or 
manufacturers’ names appear herein solely 
because they are considered essential to the 
object of this report 


78 


For impact attenuators installed in 
gore areas, 4.1 accidents per site per 
year were reported in this study. In 
many of these installations the 
attenuator was installed in front of an 
existing parapet nose which reduced 
weaving room, perhaps thereby 
increasing the number of accidents 
that occurred. In new construction 
and in some existing gores, the gore 
can be designed (or rebuilt) so that the 
attenuator occupies essentially the 
Same space as a conventional bridge 
parapet nose, alleviating this problem. 
Provision of such space in the design 
of elevated exit ramps, together with 
the installation of an impact 
attenuator, is now required on all 
Federal-aid projects (3). 


Data on vehicle heading angle and 
point of impact in an attenuator 
accident, the range of reported 
installation and maintenance costs, 
and asummary of all reported 
accidents are given in the final report 
(1). The report may be obtained for 
$3.75, paper copy and $1.45, 
microfiche (PB 224995/1AS) from the 
National Technical Information 
Service, 5285 Port Royal Road, 
Springfield, Va. 22151. 





REFERENCES 


(1) J. G. Viner and C. M. Boyer, “Accident 
Experience with Impact Attenuation Devices,” 
Final Report FHWA-RD-73-7 1, Federal Highway 
Administration, April 1973. 


(2) John G. Viner, “Experience to Date with 
Impact Attenuators,” Public Roads, vol. 36, No. 
10, October 1971, pp. 209-218. Subsequently 
published in the Transportation Engineering 
Journal of ASCE, vol. 98, No. TE1, Proc. Paper 
8747, February 1972, pp. 71-87. 


(3) “Use of Crash Cushions on Federal-Aid 
Highways,” FHWA Instructional Memorandum 
40-5-72, Federal Highway Administration, 
HNG-32, November 8, 1972. 


September 1974 e PUBLIC ROADS 


| 


’ 
: 
{ 


New Research in Progress 


The following items identify new 
research studies that have been 
reported by FHWA’s Offices of 
Research and Development. These 
studies are sponsored in whole or in 
part with Federal highway funds. For 
further details, please contact the 
following: Staff and Contract 
Research — Editor; Highway Planning 
and Research (HP&R Research) — 
Performing State Highway 
Department; National Cooperative 
Highway Research Program 

(NCHRP) — Program Director, National 
Cooperative Highway Research 
Program, Transportation Research 
Board, 2101 Constitution Avenue, 
N.W., Washington, D.C. 20418. 





PUBLIC ROADS e Vol. 38, No. 2 


FCP Category 1— Improved Highway 
Design and Operation for Safety 





FCP Project 1A: Traffic Engineering 
Improvements for Safety 


Title: Guidelines for Uniformity in 
Traffic Control Signal Design 
Configurations. (FCP No. 51A1514) 
Objective: Prepare guidelines for 
optimum traffic control signal design 
configurations at intersections and 
mid-block crossings. This must include 
considerations of cost and user 
response in terms of observance, 
safety, and efficiency. Only special 
operation techniques for special 
configurations will be considered. 
Performing Organization: KLD 
Associates, Inc., Huntington, N.Y. 
11743 

Expected Completion Date: July 1976 
Estimated Cost: $300,000 (NCHRP) 





FCP Project 1B: Remedial Driving 
Techniques for Freeways and 
Interchanges 





Title: Remedial Driving Techniques 
for Freeways and Interchanges. (FCP 
No. 31B1762) 

Objective: Determine problem 
freeway segments, identify associated 
improper and proper maneuvers, and 
develop remedial measures to 
improve drivers’ performance. 
Performing Organization: Institute for 
Research, State College, Pa. 16801 
Expected Completion Date: May 1975 
Estimated Cost: $161,000 (FHWA 
Administrative Contract) 











FCP Project 1C: Analysis and 
Remedies of Freeway Traffic 
Disturbances 





Title: Data for Development of 
Incident Detection Algorithms. (FCP 
No. 31C3514) 

Objective: Provide real-time traffic 
data on freeway incidents stored on 
magnetic tape. Obtain data at various 
volume levels on three-, four-, and 
five-lane freeways with different 
geometrics. Provide documentation 
for each incident characterizing its 
severity, type, and time of occurrence. 
Performing Organization: California 
Department of Transportation, Los 
Angeles, Calif. 90020 

Expected Completion Date: December 
1975 

Estimated Cost: $275,000 (FHWA 
Administrative Contract) 


FCP Project 1F: Energy Absorbing and 
Frangible Structures 


Title: Modifications for Achieving 
High Performance Barriers. (FCP No. 
341P 1152) 

Objective: Develop new concepts for 
low-cost impact attenuators that are 
low in maintenance, have multi-hit 
capability, utilize minimum space, 
and are high performance in design. 
Performing Organization: Eyring 
Research Institute, Provo, Utah 84601 
Expected Completion Date: June 1976 
Estimated Cost: $139,000 (FHWA 
Administrative Contract) 


FCP Project 1H: Skid Accident 
Reduction 





Title: Improvement of Utility of a 
Highway-Vehicle-Object Simulation 
Program for Highway Application. 
[FC RIING 3 12232) 

Objective: A detailed users manual of 
the present HVOSM program will be 
established. The existing programs will 
be improved for efficient utilization 
by highway personnel as well as 
extending the present capability using 
previously developed results. 
Performing Organization: Calspan 
Corporation, Buffalo, N.Y. 14221 
Expected Completion Date: December 
1975 

Estimated Cost: $115,000 (FHWA 
Administrative Contract) 


Title: Texture Measurement System 
Development. (FCP No. 31H3222) 
Objective: Performance evaluation of 
laser system for texture measurement 
under operational conditions. 
Investigation of wavelength diversity 
as measure of skid resistance at 
varying speed. Delivery of road test 
model of laser-sensor package. 
Performing Organization: Naval 
Ordnance Laboratory, Silver Spring, 
Md. 20910 

Expected Completion Date: May 1975 
Estimated Cost: $86,000 (FHWA 
Administrative Contract) 


Title: Frictional Requirements 
Necessary to Reduce Skidding 
Accident Frequencies. (FCP No. 
31H4022) 

Objective: Analysis on present data 
base and models for frictional demand 
of pavements. Design skidding tests to 
complete the data base. Semi- 
empirical modeling of skidding 
phenomena and establishing frictional 
requirements leading to an 
operational methodology. 
Performing Organization: JRB 
Associates, Inc., La Jolla, Calif. 92037 
Expected Completion Date: April 1975 
Estimated Cost: $159,000 (FHWA 
Administrative Contract) 


FCP Project 1N: Motorists’ Direction 
and Information Systems 


Title: Motorist Response to Highway 
Guide Signing. (FCP No. 51N1012) 
Objective: Identify, develop, and 
critique candidate measures of driver 
response to highway guide signing and 
develop a means for validating the 
most promising measures and conduct 
such a validation. 

Performing Organization: 
Biotechnology, Incorporated, Falls 
Church, Va. 22042 

Expected Completion Date: January 
1976 

Estimated Cost: $250 000 (NCHRP) 


FCP Project 10: Aids to Surveillance 
and Control 


Title: Structural and Geometric Design 
of Highway-Railroad Grade Crossings. 
(FCP No. 4101042) 

Objective: Develop implementable, 
structural, and geometric design 
criteria for highway-railroad grade 
crossings. 

Performing Organization: Texas 
Transportation Institute, College 
Station, Tex. 78701 

Funding Agency: Texas Highway 
Department 

Expected Completion Date: August 
1927, 

Estimated Cost: $170,000 (HP&R) 


FCP Category 2— Reduction of Traffic 
Congestion, and Improved 
Operational Efficiency 





FCP Project 2B: Development and 
Testing of Advanced Control 
Strategies in the Urban Traffic Control 
System 





Title: UTCS/BPS Software Support. 
(FCP No. 32B2512) 

Objective: (1) Integrate advanced 
traffic control strategies with the 
UTCS-1 simulation; (2) test advanced 
traffic control strategies; (3) convert 
housekeeping software associated 


80 


with the second generation software 
into FORTRAN IV; and (4) code, 
integrate, and test third generation 
software. 

Performing Organization: Honeywell, 
Inc., Hopkins, Minn. 55343 

Expected Completion Date: December 
1975 

Estimated Cost: $581,000 (FHWA 
Administrative Contract) 


FCP Category 3— Environmental 
Considerations in Highway Design, 
Location, Construction, and Operation 


FCP Project 3F: Pollution Reduction 


and Visual Enhancement 


Title: Erosion Control During Highway 
Construction. (FCP No. 53F1592) 
Objective: Assess methods of erosion 
control currently in practice; develop 
a manual recommending techniques 
to reduce erosion; identify research 
needs in the research area. 
Performing Organization: Utah State 
University, Logan, Utah 84321 
Expected Completion Date: October 
1975 

Estimated Cost: $175,000 (NCHRP) 


Title: Establishment and Management 
of Vegetation in Highway 
Environments. (FCP No. 43F1732) 
Objective: Establish habitat 
restrictions and develop procedures 
for establishing plants for erosion 
contro}. Develop methods for 
controlling unwanted plants. 
Performing Organization: Texas 
Transportation Institute, College 
Station, Tex. 77840 

Funding Agency: Texas Highway 
Department 

Expected Completion Date: August 
1978 

Estimated Cost: $150,000 (HP&R) 





September 1974 e PUBLIC ROADS 





FCP Category 5— Improved Design to 
Reduce Costs, Extend Life Expectancy, 
and Insure Structural Safety 


FCP Project 5D:Structural 
Rehabilitation of Pavement Systems 





Title:Pavement Evaluation. (FCP 
No. 35D1022) 

Objective:Develop methodology 
for the determination of a pavement’s 
structural adequacy taking into 
account the load-carrying capability, 
serviceability, and remaining life of 
the structure. 

Performing Organization: I exas 
Transportation Institute, College 
Station, Tex. 77843 

Expected Completion Date: 
February 1977 

Estimated Cost:$204,000 (FHWA 
Administrative Contract) 


Title:Reconditioning Heavy-Duty 
Freeways in Urban Areas. (FCP No. 
55D2172) 

Objective:Develop a new 
technology for reconstituting and/or 
replacing all or part of the pavement 
structure on a heavily traveled urban 
freeway so that the finished product 
has a design service life equal to or 
greater than that of the original 
pavement, including restoration of 
riding and non-skid characteristics. 
Performing Organization: I exas 

A&M Research Foundation, College 
Station, Tex. 77843 

Expected Completion Date:QOctober 
1975 

Estimated Cost:$100,000 (NCHRP) 





- FCP Project 5F: 
Inspection 


Bridge Safety 





Title:Acceptance Criteria for 
Electroslag Weldments in Bridges. 
[PCr No. 55F2112) 

Objective:The fracture and fatigue 
crack growth behavior of the heat- 
affected zone and various areas within 
the fusion zone of electroslag 
weldments will be studied. The 


PUBLIC ROADS e Vol. 38, No. 2 


influence of base material (A36 and 
A588 steel) plate thickness (1- and 4- 
inch) as well as numerous process 
variables are included in the 
experiment design. 

Performing Organization:U.S. Steel 
Corporation, Monroeville, Pa. 15146 
Expected Completion Date: April 
1976 

Estimated Cost:$200,000 (NCHRP) 


FCP Project 6Z:|mplementation of 
Research Projects 


Title:| mplementation of Research 
(FCP No. 4621733) 
Objective:Special efforts to insure 
that the results of research and 
development projects are brought into 
operating practice. 

Performing Organization:New York 
Department of Transportation, 
Albany, N.Y. 12226 

Expected Completion Date:May 1975 
Estimated Cost:$87, 000 (HP&R) 


Title: Determination of Tolerable 
Flaw Sizes in Full Size Bridge 
Weldments. (FCP No. 35F2132) 
Objective:Experimental 
determination of the tolerable fatigue 
crack size in bridge girders and gusset 
plated truss connections. Correlation 
of experimental results with analytical 
determination of stress intensity factor 
and measured material toughness. 
Performing Organization:Lehigh 
University, Bethlehem, Pa. 18015 
Expected Completion Date: 
December 1975 

Estimated Cost:$245,000 (FHWA 
Administrative Contract) 


FCP Category 6— Development and 
Implementation of Research 





FCP Project 6C: Traffic Engineering 





Title: Traffic Responsive Ramp 
Control Through Use of Micro 
Computers. (FCP No. 46C1173) 
Objective:Evaluate the use of micro 
computers as traffic responsive ramp 
controllers. Work includes 
development of both hardware and 
software considering both cost and 
functional capability. 

Performing Organization:California 
Department of Transportation, 
Sacramento, Calif. 95814 
Expected Completion Date: 
December 1976 

Estimated Cost:$122,000 (HP&R) 





New 
Publications 





Motor Carrier Safety Regulations 
provides, in one publication, the 
applicable motor carrier safety 
‘regulations for motor carriers 
operating in interstate or foreign 
commerce. This is a revised issue of 
the regulations, including 
amendments through October 1, 1973, 
parts 390 through 397. There are 

{ore olatolamelUr-lititer-tdlolat mel melah alae 
driving of motor vehicles; parts and 
accessories necessary for safe 

ue) elie ha lelabmarelaiacer-ldlolaMmccloleladlat-ae-lave| 
recording of accidents; hours of 

SY olaVilel-Me) mel dhl em laltel-edlelalr-late 
lnatellahcciar-lel@chin de-lalyolelae-lalelame)i 
hazardous materials; and driving and 
parking rules. 


Lisle wolelelite-lalolamaat- Wa elem elll cel al-CicteM (ols 
a BVAOR icolesmaatcmiel ol-lalalcclale(slalmeyi 
Documents, U.S. Government Printing 
Office, Washington, D.C. 20402 (Stock 
Number 5004-00010). 





Part VI, Traffic Controls for Street and 
Highway Construction and 
Maintenance Operations, of the 
IAFetalUE-tolpm Olalicelseaml Ne-ind{en Qolatace)| 
Devices has been reproduced as a 
separate publication to meet the 
aleve ko) mi ae-ta stom @olalace) mie-lalel-lnemiole 
rol ah ja qu reidlolapmaar-lialeciar-lalecme-lalomelalliay 
Wield ar-lgcr-CMlamaalem OlalicsteMsie-lesom 2-171 
VII, Traffic Controls for School Areas, 
(o) MaaTomAtclalel-1 Mm at-Cer-l Ko of-tclam 010] oli Kval-ve| 
separately for the special demand of 
Vialhtoldaamae-lhicemee)alacelmie-laler-lcecula 

ol stole) -lccy-CudalcoleyedslolUlamdal-MN Tr lelolan 
stolaamye-lalel-lnekw-lccm-l ole) [fe-10)(-mcol-1 1 
public roads regardless of type or 
class, or agency having jurisdiction in 
accordance with Federal legislation. 


1h OYA olam Glolakiaguoidie)al-lare| 
Maintenance Operations may be 
purchased for $1.25 (Stock Number 
lO OME O0 Clow DE-lalem ot-1 aan Val Mola i ielalole)| 
Areas for 75 cents (Stock Number 
5001-00067) from the Superintendent 
of Documents, U.S. Government 
Printing Office, Washington, D.C. 
20402. 


82 





Highway Transportation Research and 
Development Studies 1973 presents a 
complete inventory of the research 
Flare me (enVci(o) olaateralaciaulol(ecw-lolelco\Zcrommla 
progress, or completed during fiscal 
year 1973. The report contains 
individual vignettes for all research 

El aremoleacl(o)olaatcialaciaerel(<cmdat-larlac 

10] 0) oLelaacrem-lalem-I(e(stom on manic motels) ec) 
Highway Administration’s Offices of 
exits gel ai-lalom DL=aV2l Ke) olantclalam siulactl0 Me) i 
Kol ol al F-laal-lamsy-licia AelaleRct=) (tei cee! 
fole-lalalialea cexter-1 cel smciae lel (= micelaameats) 
Offices of Planning. 


ibalkmoleio)iter-lalolamimlalcciare(crem elalantelai hy 
irolmaatemiaicoldnar-ldlelam-lalem+i0ller-laleaome) | 
Federal and State personnel 
concerned with highway-related 
research, particularly those in the 
Federal Highway Administration 
Gah a0 ic lale Rolagtciar-tsiclalel(scmWaiaeliamaatsy 
Oye Di-ley-laennlalmolm Me-lariolelacclarela 
(DOT), and those in State highway 
departments or departments of 
transportation. It will be useful also to 
other Federal and local government 
personnel; to highway-oriented and 
Wie) altel (mrolalclahecremagc(e(-¥molcelis\s (earl ip 
and research organizations; and to 
members of the general public 
interested in or concerned with 
iexter-l cel eM famallsdaiwz-Wade-lattelelae-lalelae 


WM alkmolelo)iver-tdlolamant-\vm olen oll lane atcKi-vem (els 
$4.50 from the Superintendent of 
Documents, U.S. Government Printing 
Office, Washington, D.C. 20402 (Stock 
Number 5003-00157). 


September 1974 e PUBLIC ROADS 





. 





The following highway research and 
development reports are for sale by 
the National Technical Information 
Service, Sills Building, 5285 Port Royal 
Road, Springfield, Va. 22151. 


Other highway research and 

development reports available from 
the National Technical Information 
Service will be announced in future 


issues. 


STRUCTURES 


Stock No. 
PB 226625 


PB 226884 


PB 228329 


PB 228680 


PB 228681 


PB 228720 


PB 228786 


PB 229401 


Analysis of Overhead Cable- 
Supported Roadway Sign. 
Development of Louvered 
Signs to Reduce Wind Load. 
An Investigation of the Load- 
Carrying Capacity of Drilled 
Cast-in-Place Concrete Piles 
Bearing on Coarse Granular 
Soils and Cemented Alluvial 
Fan Deposits. 

Field Measurements of Lateral 
Earth Pressures on a Pre-Cast 
Panel Retaining Wall. 
Condition of Longitudinal 
Steel in Illinois Continuously 
Reinforced Concrete 
Pavements. 

Fill Stabilization Using Non- 
Biodegradable Waste 
Products— Phase |. 

Barrier VII: A Computer 
Program for Evaluation of 
Automobile Barrier Systems. 
Design Variables for Cut 
Slopes. 


PUBLIC ROADS e Vol. 38, No. 2 


Highway Research and 
Development Reports Available 
from National Technical 
Information Service 


PB 


PB 


PB 


PB 


PB 


ea 


PB 


PB 


PB 


PB 


PB 


PB 


PB 


PB 


PB 


PB 


83 


229509 


229611 


229720 
229885 


229977, 


Patera bo beh) 


229948 


230449 


230847 


230940 


230942 


231173 


231178 


231202 


251219 


231326 


231350) 


Evaluation of Stud Welding 
System for Aluminum 
Highway Signs. 

Live Load Stresses in a Straight 
Box-Girder Bridge. 


Skid Test Trailer Calibration. 
Computer Evaluation of 
Automobile Barrier Systems. 
Feasibility Study and 
Preliminary Design of a System 
for Rapid Evaluation of 
Rational Pavement Designs. 
An Analysis of Dynamic 
Displacements Measured 
Within Pavement Structures. 
Load Distribution ina 
Composite Steel Box-Girder 
Bridge. 

Probabilistic Design Concepts 
Applied to Flexible Pavement 
System Design. 

The Rehabilitated AASHO Test 
Road, Part |— Materials and 
Construction. 

Analytical Problems in 
Modeling Slurry Wall 
Construction. 

Investigation of Dynamic 
Stresses in Highway Bridges — 
An Interim Report. 
Development of Guidelines for 
the Design of Subsurface 
Drainage Systems for Highway 
Pavement Structural Sections. 
Evaluation of Existing Bridge 
Expansion Joints. 

Proceedings of a Symposium 
on Downdrag of Piles. 

A Study of the AASHO Road 
Test—Final Summary Report; 
Phase 2— Evaluation and 
Application of the AASHO 
Road Test Results. 
Correlation of Pavement 
Behavior and Performance 
Between the University of 
Illinois Test Track and the 
AASHO Road Test. 
Pavement Design and 
Performance Study; Phase B— 
Deflection Study: Interim 
Report No. 5, Nuclear 


Measurement of Subgrade 
Moisture. 


PB 231998 Creep and Shrinkage Study of 


Concrete Made from Hawaiian 
Aggregates — Phase II. 


MATERIALS 


Stock No. 


PB 


PB 


PB 


PB 
PB 


PB 


PB 


PB 


PB 


PB 


PB 


PB 


PB 


PB 


PB 


228330 


228679 


228975 


228976 
228982 


228993 


229744 


2290.11 


230951 


230953 


230986 


230990 


231000 


231021 


231208 


Application of Electro-osmosis 
to Marginal Soils. 

The Effect of Sodium Chloride 
on the Corrosion of Concrete 
Reinforcing Steel and on the 
pH of Calcium Hydroxide 
Solution—Interim Report. 
Technical Control of Sulfate 
Waste Materials at the Transpo 
EA Ze oite! 

Structure Backfill Testing. 
Behavior of Shrinkage- 
Compensating Concretes 
Suitable for Use in Bridge 
Decks — Interim Report, Phase]. 
Investigation of Lime Slurry to 
Control Absorptive Aggregates 
Used in Asphalt Concrete. 


Traffic Stripes and Formed-in- 
Place Delineators. 


Electrical Resistivity 
Techniques. 

Arkansas Waste in Municipal 
Areas Suitable for Highway 
Construction or 
Maintenance —Final Report. 
The Location and Potential 
Highway Use of By-Products in 
Arkansas—Final Report. 
Experimental Cathodic 
Protection of a Bridge Deck. 
Bridge Deck Membranes — 
Evaluation and Use in 
California—Interim Report. 
First Progress Report on 
Concrete Experimental Test 
Sections in Brazos County, Tex. 
Wet Night Visibility— Interim 
Report. 

Accelerated Environmental 
Testing. 


PB 231243 


PB 231388 


PB 231649 


PB 231908 


PB 231965 


id ay ok Lede 


TRAFFIC 


Stock No. 
PB 228421 


PB 228423 


PB 228516 


PB 2o350 


PB 229886 


be 229903 


PB 230047 


PB 230448 


PB 230760 


PB 230761 


PB 230762 


PB 230763 


Paint Characterization by 
Electrical Techniques. 


Refinement of Moisture 
Calibration Curves for Nuclear 
Gage. 

Failure Modes and Required 
Properties in Asphalt- 
Aggregate Cold Mix Bases. 


Evaluation of Interior and 
Exterior Latex Paints. 


Design Considerations for 
Asphalt Pavements. 


Skid Resistance and Wear 
Properties of Aggregates for 
Paving Mixtures. 


Freeway Operations Study — 
Phase Ill. The FREQ3 Freeway 
Model. 
Optimization Techniques 
Applied to Improving 
Freeway Operations. 
Meaning and Application of 
Color and Arrow Indications 
for Traffic Signals —Final 
Report and Appendices. 
Diagrammatic Guide Signs for 
Use on Controlled Access 
Highways: Volume II — 
Laboratory, Instrumented 
Vehicle, and State Traffic 
Studies of Diagrammatic 
Guide Signs. 
The Improved Effectiveness of 
Traffic Signal Systems: 
Conventional Signal Network 
Timing Strategies. 
Information Lead Distance 
Studies — Electronic Route 
Guidance Systems. 
Computer Control of the 
Wayside-Telephone Arterial 
Street Network. 
The Improved Effectiveness of 
Traffic Signal Systems: 
Effects of Changes in Signal 
Operation on Traffic Flow. 
Network Flow Simulation for 
Urban Traffic Control 
System — Phase II. 
Vol. 1— Technical Report. 
Vol. 2— Program 
Documentation for UTCS-1 
Network Simulation Model, 
Part |. 
Vol. 3—Program 
Documentation for UTCS-1 
Network Simulation Model, 
Part Il. 
Vol. 4— User's Manual for 
UTCS-1 Network Simulation 
Model. 


PB 230764 


PB 230996 


231042 


RB 23105 


PB 231077 


PB 231086 


PB 231161 


Vol. 5—Applications Manual 
for UTCS-1 Network 
Simulation Model. 
Right Turn on Red. 
Feasibility Investigation of 
Audio Modes for Real-Time 
Motorist Information in Urban 
Freeway Corridors. 
Cost Effectiveness Evaluation 
of Freeway Design 
Alternatives — Freeway 
Operations Study, Phase II]. 
Development of a Model for 
Predicting Travel Time on an 
Urban Freeway. 
Dallas Corridor Frontage Road 
Evaluation Plan. 
Progress Toward a Freeway 
Corridor Model— Freeway 
Operations Study, Phase III. 


ENVIRONMENT 


Stock No. 
PB 228517 


PB 229334 


PB 229605 


PB 229610 


PBEZ2 3030 


PB 230995 


PB?230999 


PB 231074 


PB 231104 


PB 23 1387 


PB 231583 


PB 231889 


84 


Summary and Assessment of 
Sizes and Weights Report. 
Evaluation of a Method of Fog 
Dispersal by lonization. 
Hydraulic Performance of 
Pennsylvania Highway 
Drainage Inlets Installed in 
Grassed Channels (Type H, 
Type 4-ft and 6-ft). 

Lensed Rail Lights for 
Pavement Illumination. 
Procedures and Materials for 
Roadside Development in 
Montana. Interim Report: 
Dryland Sodding with Native 
Grasses for Permanent Erosion 
Control. 

Hydraulic Performance of 
Bridges — Efficiency of Earthen 
Spur Dikes in Mississippi. 
Species Recommended for 
Highway Plantings Selected 
from a Natural Vegetation 
Survey in the Panhandle of 
Nebraska. 

Stabilizing Disturbed Areas 
During Highway Construction 
for Pollution Control. 

A Minimum-Cost and 
Environmentally-Safe Program 
of Herbicide Maintenance for 
Indiana Roadsides. 

Manual of Procedures for 
Conducting Studies of the 
Desirable Limits of 
Dimensions and Weights of 
Motor Vehicles. 

A Simplified Procedure for 
Computing Vehicle 
Offtracking on Curves. 
Colorado Tunnel Ventilation 
Study. 


IMPLEMENTATION 


Stock No. 


PB 228448 Determination of the 


PB 228449 


PB 228473 


PB 228511 
PB 228572 


PB 228656 


PB 229824 


PB 230381 


PB 230497 


PB 231018 


PB 231159 


PB 231382 


PB 231552 


PB 231818 
PB 231890 


PB 231891 


PLANNING 


Stock No. 
PB 228997 


PB 231168 


PB 231594 


Feasibility of Using Southern 
Pine Veneer Log Cores as Posts 
for Fencing Highway 
Projects—Final Report. 

An Investigation into the 
Gradation Variability of 
Aggregate Used in Bases. 
Modern Concepts for Density 
Control. 

Phase |: Bituminous Wearing 
Courses. 

Tunnel Cleaning Method. 
Construction Control of Rigid 
Pavement Roughness —Final 
Report. 

Recordation of Quantities of 
Materials Incorporated in Base 
and Pavement Plant 
Mixtures—Final Report, 
Phase II. 

Microwave Heating for Road 
Maintenance. 

Modification and Calibration 
of the Illinois Skid Test 
System. 

Skid-Resistant Characteristics 
of Experimental Bituminous 
Surfaces in Illinois. 
Variation of the Results of 
Routine Concrete Tests Using 
Standard and Accelerated 
Curing Methods. 

Modern Concepts for Density 
Control— Phase II: 

Granular Base Courses. 
Variations in Portland Cement 
Concrete Construction in 
Nebraska. 

Modern Concepts for Density 
Control— Phase II: 
Embankment Materials. 
Texas Crash Cushion Trailer. 
Bridge Rating and Analysis 
Structural System (BRASS). 


Vol. |.—System Reference 
Manual. 
Vol. 1l—Example Problems. 


Studies of Optimal Models of 
Interchange Development 
Through Land Use Regulation 
and Control. 

Test and Evaluation of Data 
from the Standard Package of 
Census Data for Urban 
Transportation Studies. 
Design of an Information 
System for Continuing 
Transportation Planning in the 
Albuquerque Metropolitan 
Area. 


*U.S. Government Printing Office: 1974—620-830/4 


Sept 


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